I'm suspicious that in development they had some memory corruption bugs (which of course they fixed), and they decided to force the same bugs with the piracy detection.
@@pfcrow No way, this is 100% intentional. Using the low byte of the player score is a cheap source of randomness. All of these tricks are designed to be difficult to debug, and I take my hat off to the elegant malevolence of their author. I once had to solve a similar problem of building a cheater-detection algorithm in a javascript game where it would be trivial for lots of people to inspect the minified-then-reexpanded source code. It was similar because all of my mechanisms would be in code that my opponent could freely read and inspect, so security through obscurity is the name of the game. In my case, the cheater's modified code would be sending a fraudulent game state to a server where it would then become visible to the honest players. I figured most cheaters would try to hack the bytes being sent to the server without tracing all the way through the code to find their origination, so as deep as possible down the stack I computed a checksum of the game state and stored it in the nanoseconds digits of a timestamp that existed primarily to serve this purpose. A user could then hack the score report being sent to the server, and it would seem to work, to them, but unbeknownst to them the checksum mismatch would be detected on the server and their account would be segregated into a "cheaters only" pool where their bad behavior couldn't discourage honest users. It might take them some time to figure out that their account had been poisoned, at which point they'd had no idea how it happened. And debugging it would require constantly generating new user accounts. It could be done, but would take a rare level of dedication. Point is, you want to separate the method from the action, such that the code doing the check lays a landmine that doesn't explode until later so that when the black-hat debugs into the problem, there are no obvious hints as to how and why the bad state came to be. They then have to run the code again watching for changes to a memory address, but maybe the next time the landmine is laid elsewhere. You might have to build special-purpose debug tooling to ever figure it out.
Although with arcade games, it really feels like punishing the player, who just came into the arcade and tossed in a quarter, when they would have had nothing to do with the pirating. All the while, who ever put together the counterfeit cabinet or sold the board to put into a bare one, still made money on it, so these tactics likely didn't do anything to stop those actual pirates. So like with more modern DRM from recent decades, it's end users who give their money to play who get screwed by the game's maker (and/or publisher.) Edit: typo
@@imveryangryitsnotbutter What they did was essentially screw up your save as time went on. And the same thing is done in Earthbound on SNES. However, that game also resets all your progress when you go to the final boss.
These "slow pirates down so much that people early on are just going to buy the dang game" are so cool. It's sad that they've fallen out of fashion but... that's also literally what modern anti-piracy does. Denuvo is possible to crack, but it takes weeks for the One Person Who's Capable Of It to manage it-if you follow modern games and piracy, you'll notice that most of the hype around a new game will have died down before cracked copies are available. When a lot of modern games live or die on their first week of sales, just stopping people pirating for a fortnight makes a ton of difference. Denuvo just does it with complicated and weird maths, rather than making the game slowly fuck up as time goes on , but the impact to pirates and consumers of pirated games is the same.
one reason why they likely bound the checksum to the copyright notice specifically is that it gives them an extra legal avenue to pursue in that they aren’t just altering the code to work, they would have to fraudulently misrepresent something with altered copyright information as that’s the only valid set of values. that’s why for example, the sega genesis would display ’licensed by sega’ etc, because an unlicensed game would cause that message to display and essentially become a legal claim. there were some interesting court cases around this, and i imagine the copyright notice here being the checksum serves a similar function.
Nintendo tried something similar with the GameBoy, since the logo is loaded off from the Cartridge, and displayed on the screen. If the logo shows up correctly, a check passes and it boots up normally, if it doesn't, it doesn't boot. However, pirates found out how to bypass the check by changing the values the check sees compared to the ones being displayed, so if you see any Cartridge displaying a logo other than Nintendo's and still booting up, now you know why.
I remember that Sega's implementation was tested in a court. The affected party claimed that the licensing message was just a techical requirement to get games to work and not actual violation of the trademark, and the court agreed. But this happened years after Tempest was released.
Yep, that’s Sega v. Accolade case from ’92. However, in this situation this wouldn’t work the same way since there is no hardware or firmware check that the copyright notice exists. It’s likely more so that it’s hard to remove the notice and having the notice makes it simple to notice and prove that the code was copied.
Makes sense, iirc back in the 80s legal protection for software was pretty much nonexistent so relying on the "classic" copyright laws was probably the only way to get some protection at all.
@@mina86 true. absolutely not a 1 for 1. i just imagine if atari sniffed out an arcade or distributor or whatever 'altered attribution' or something it could be an extra thing to tack on. it would make it harder to plead ignorance at any rate.
The checksum mattered to ATARI because pirates would remove copyright messages, allowing arcade owners and bootleg manifacturers to go "but I didn't know" by "forcing" copyright messages, ATARI could then point to the copyright notice, and claim that they had to know, they were told on the title screen.
Also, it means even if you have a bootleg Tempest cabinet in your arcade, it still shows Atari's name to everyone in the arcade, including anyone who sees the game and decides they want to buy it for *their* arcade, so Atari still has a shot at getting some sales out of it.
One fun thing about the graphical glitches, if displayed on a real machine there is a chance the monitor will be damaged. WG K6100s are pretty delicate, if the deflection input is out of range (ie drawing shit outside of the normal bounds of the screen) it can cause too much current to flow through the transistors that drive the yoke, causing them to short, blowing out the voltage regulator transistors and causing you to have a very sad monitor. Almost anyone who has or had a color vector atari machine knows the pain. They're pretty annoying to repair.
With how formal and instructive your videos always are, that little "...apparently" caught me off guard, I probably laughed much harder than I should have
I once went to an arcade, it’s probably been five years since this happened, but it was one of those typical “we put smartphone games on a bigger screen and called it a day” type of arcades. Yet, for some reason, literally sitting UNDER a set of stairs, there was a Tempest machine. You know damn well what ensued afterwards. Best arcade I’ve ever been to, not that that’s saying much, since most of them don’t even have anything besides the aforementioned smartphone games, and I haven’t been to all that many. (By the way, this wasn’t some reproduction or an emulator in a box. It was a genuine musty old piece of work, and why it was in this place, I have no clue.)
I hate those giant smartphone games. I went back to an arcade of my youth expecting to see the faithful old HOTD 4 and Mario Kart Arcade GP 2 machines and there they were. It hurt.
I remember during a behind the scene video about Tempest, there was a glitch/failsafe that if the copyright wasn't in a specific place, the game would automatically add a large number of free credits. this kept machine owners/renters form using unlicensed products.
I think I've heard the same thing about Asteroids. Though, that one also had a "trick" where people would get down to a single small asteroid and spawn-camp the small ships, racking up insane points and lives. Enough to be able to take a bathroom break during marathon sessions, for instance. Arcade owners didn't like that, since they were playing on a single quarter.
Tempest has a brilliant hidden feature in the v1 and 1.1 versions of the game back in 81. I stumbled across it while playing it in the arcade then never spent more than a quarter ever playing it from then on. You ensure that the last two digits of your score ended with a specific value, then let the game and go back to demo mode. At the second loop of demo mode the game would then react depending on the digits. 99 free games, ability to start at any level, unlimited deaths etc. It was intentional - a thank you to us obsessive players.
It is interesting that if the game's software or hardware is modified, you will still have a free trial, but then the game breaks completely after the trial ends.
By putting antipiracy checks at difficult levels, they all but guarantee that the pirates who are good at messing around with the code but likely not experienced Tempest players, won't trigger it. Then they get the joy of deploying a bunch of these clone cabinets and then the complaints pour in from arcade owners when players keep complaining that the machines are crashing. This would be far less of a nuisance if the pirates knew there was a problem before they manufactured and sold a bunch of these things.
This was rather interesting. Years ago I was quite heavily involved involved with software and hardware development on PCs. One anti piracy technique I developed was based on floppy disk storage. The way data is normally stored on disk is as a series of Sectors on each track. Each sector is numbered but generally, not (as you might expect) in order. Instead, the sectors were arranged so that, after reading the sector No 1, you'd skip the next and then the sector after that would be Sector No. 2. This would give the bios time to be able to process the first sector before reading the second. After a complete rotation of the disk, you'd then have half of the sectors on that track. A second revolution would follow the same pattern but reading the alternate sectors that had been skipped on the first revolution. So it would take two complete revolutions of the disk to read one complete track. This was actually faster than having the sectors in order because if the bios missed the beginning of just one sector, it would have to wait a full revolution of the disk to get back to the missed sector. Having an intervening sector made this less likely to happen. Now for my anti piracy method, I'd run a custom low level format on the disk, such that one track (eg. track 7) had all the sectors stored in reverse order. This made the time to read that track take much longer to read than any other track. (typically 16 revolutions of the disk compared to 2). Once the disk had been put through this low level format, it could be written to in the normal fashion but when reading that track, it would take 8 times as long to read, compared to the other tracks on the disk. If anyone ever used standard tools to copy the disk, all the data would be perfectly copied over BUT, when reading that track, it would read at the same speed as any other track. Thus giving away that it was not an original copy. The beauty of this was that the client could even format the original disk (using the dos Format command) and download an updated version of the software and write it to the disk and it would still work. (formatting doesn't overwrite the low level format, it uses the existing sector markers). So effectively, there was nothing to see in the software, it was the disk itself that had been "marked" as authentic. I used some similar methods on CDs and obviously we had other techniques at our disposal. I was asked to implement a process that would copy the serial number of the CPU onto the floppy disk on first setup to bind the software to that one machine, but I refused to implement that, as I felt, if someone has paid for a copy of the software, they should be allowed to upgrade their machine without loosing functionality of our software.
Lots of Apple II titles also did wonky things to the on-disk format (resizing sectors, changing required spindle speeds for specific tracks, etc.) so as to make it more difficult to produce working copies even if you had the binaries. The Apple didn't have a "smart" disk controller and did everything in software with the CPU, so it was possible to make the drive physically do all kinds of weird things to accommodate non-standard protected disk formats.
@@stevepreskitt283 I also used to write the BIOS routines to access disk drives. One of the easter eggs I put into one of our bios chips allowed you to play a tune on the floppy drive. It was quite a crude routine that just drove the head stepper motor at the required frequencies. This was discovered by my boss when he asked me "Why is my floppy drive playing La Marseillaise?" I then informed him "That's odd, it should be playing the intro to All You Need Is Love"
Wow, this is absolutely diabolical! As a kid I used to crack 8-bit computer software, and once the idea of delayed validation occurred to me, it was always in the back of my mind. I only ever found one case, though - a cartridge game that clobbered itself with garbage at random intervals to thwart RAM-based execution. I think this sort of thing was rare because protection was usually bolted on by the publisher rather than baked in by the developer. Anyway, thanks for the amazing video!
I would assume that the reason the checksum only checks the atari copyright text is so that anyone who makes an illegitimate copy of the game can be sued on the grounds of copyright infringement, similar to how nintendo used their logo for legal copy protection for the gameboy.
The Gameboy case was interesting, but was designed to prevent unlicensed games rather than piracy. The logo WAS the key, so there was no obvious way to make a compatible game without displaying the Nintendo logo and committing trademark infringement. One company ultimately designed a cartridge that switched memory banks so the real logo would be read for the check and there's would be read for the display, even though the GameBoy thought it was reading from the same location. Nintendo tried to sue them for copyright infringement for even having their logo data in their code, but the game maker won because the only way to make a compatible product was to include that data. It would be like Microsoft suing you for including PE headers in your program
@@niko5008 it does add a significant amount of complexity to the cartridge though, which increases any unlicensed games cost due to both more expensive cartridge hardware and r&d costs
@@sircalvin they could just put some RAM in the gameboy that save the logo so they can be read twice with no problems. Or maybe just check the ROM and write it in the vram at the same time so it can't be bank-switched so easily.
...and that means the rest of "anti-piracy screens" in videogames are fake as some type of videos showing false and not accurate "anti-piracy screens" which most of them are maded with modern hardware and software, most common video editors, image editors or music production software for try to recreate it? I mean, although the Tempest one it's really impressive for a game I don't know games with methods almost comparable or superior, if you want some real anti-piracy screens check out most of the classical "Error: Pirated copy" text or something in a plain background.
I love these types of videos. Do you think you could take a look at how Earthbound anti-piracy measures work? It has a pretty devious payload of wiping save data. It also shows some random corrupted visuals and sound effects that seem to be different every time, so I've always been curious about how exactly it works.
turning on decimal arithmetic is hilarious, that's my favorite one! 😆 I also really like the hardware RNG function in general, making crappy RNG values but doing it really frickin fast so it's good enough to work. I haven't researched this era of games very much so i never saw that before, i'm more used to NES/SNES RNG where it's in software. Spyro 3 also famously has a bunch of individual anti-piracy checks that are triggered at different points in the game to make it frustrating for hackers to bypass them, making the game just slowly get less playable over time. I don't recall the exact method used for the checks though, but there's probably a dozen videos about it.
pseudo rng is still the most common. True random numbers are generated by non-deterministic things which circuits are incapable of. Id look at tom scott’s lava lamp that keeps the internet safe video
Yeah, I've heard of Spyro 3's anti-piracy measures, and Mother 2/EarthBound's anti-piracy measures are really interesting too. If I remember right, when making a new save file, the game checks the amount of RAM on the cartridge, and if the RAM amount is incorrect _(because bootleg carts usually have more RAM than legit carts),_ it makes the enemy spawn rate EXTREMELY high and also places enemies in locations that don't normally have enemies _(e.g. Onett after beating Frank),_ causing EarthBound to become nearly unplayable. Oh yeah and it also crashes and deletes all of your save files if you manage to make it to Giygas
It was a common practice for bootleggers to alter or erase copyright strings in games. I remember reading on TCRF the ways Konami would put anti-piracy checks in their late-gen NES games and the way they'd mess with the player if they were tripped, such as making Super Shredder invincible in TMNT3 so you couldn't beat the game. In all those cases, it was the removal of the word Konami that triggered the check, so what Atari did for Tempest is not that unusual.
And then Russian kids would be wondering in frustration why can't they beat Shredder when they bought the game from Steepler on a licensed Dendy cartridge.
Similarly for cracks of home videogames, the crack group would put their names and greets to other crack groups in the game (this eventually became the demoscene). While any half decent cracker would just remove these checks, you would assume the theory was to catch crackers out when they gloated about cracking the software.
LFSR was used by David Crane who wrote the game Pitfall to generate random yet repeatable scenes/pages within a game when moving left or right. It was mainly done for saving memory in those early machines, rather than drawing out each scene/page individually. It was quite clever and worked great. ;)
For anyone wondering why the copyright string is so specifically protected, it was common practice in the day for bootleg arcade machines to alter the data, which at the very least would generally include a different title and copyright string. Essentially this was done in the hope that they could technically say, for example, "we weren't distributing unauthorized copies of Mario Bros, this is _Pest Place!"_
@@silkwesir1444 That was the logic that game bootleggers were attempting to make it look like their "products" fell under. However, the fact remains that the _code_ is still proprietary, and bootlegs still lift the code without permission, no matter how much the branding is dolled-up to look different (as opposed to clones, which are clean recreations of the mechanics without stealing the code).
Honestly games just messing with you instead of just stopping you from playing at all is my favorite type of this Earthbound also did this where enemy spawns get greatly increased and the final boss crashes the game and resets your save before you can beat it
The piracy check definitively is interesting with the side effect it also caught emulators and is almost like an accidental forethought of anti-emulation like performing a division on the SNES when the result is not ready (which would trigger ZSNES, an emulator infamously known for its inaccuracy like instant arithmetics). The last phrase when you mentioned your supporters also is a very good point given that DRM measures are bound to be broken and thus mainly focus on the release (where the hype is typically the largest) and coding knowledge of the game is naturally the smallest for any outsider. The software protection also made me realise that according to some Discord messages or UA-cam comments, pirated SNES games often are dumped on cartridges which have more than enough to not deal with not having enough RAM which in turn also has been used for anti-piracy measures by taking advantage of mirroring. As a realistic example, a game comes with 8KiB ($2000 bytes or the mapped address range $0000-$1FFF) of cartridge RAM stores some value at $1FF0 and then a different value at $7FF0 (which is valid for 32 KiB or $8000 bytes of memory / has the range $0000-$7FFF). By mirroring, $7FF0 is reduced to $1FF0 (because $7FF0 & $1FFF or $7FF0 % $2000 = $1FF0) on the 8 KiB cartridge. It then compares the latter value with the one of $1FF0 and if both are unequal, it means the game has more RAM than it's intended and thus must be pirated.
Super Mario 64 not crashing on officially emulated rereleases when the camera enters a parallel universe is also this. The Wii/U/Switch uses its own FPU rather than emulating the N64's; and their FPUs don't have the glitch that causes the crash.
Few if any SNES games actually used division and multiplication for this check. IIRC Byuu himself mentioned that BSNES doesn't use it by default because it's inconsequential in practice when dealing with official games.
@@fungo6631 That's why I mentioned "accidental forethought" (or rather, accidental futureproofing") in the OP because most pirates used physical cartridges and original hardware while emulators became important only later on. It's also very much a thing in BSNES to accurately calculate mult/div with at least the version I use so the information you have are likely outdated.
@bensmith3890The GBC only checked the top half of the logo, as well. Also, there were some clever workarounds based on the fact it was loaded into vram and then checked afterward, meaning that if you supplied your own logo for the first one and then swapped it back to the Nintendo logo for the second one it'd still boot properly while showing something different onscreen.
Would any pirate leave the copyright information intact? I doubt they'd want to advertise that they are ripping off the owners. So of course they will get rid of it,
It's a legal cover-your-own-ass move, iirc. Sharing pirated games or romhacks was a legal grey area back then, but copyright infringement is *not* so legally grey. It gave atari a much easier avenue to go after pirates.
Final Fantasy 1 does a similar check on the programmer's name on the title screen. It's much more obvious though; the game just freezes when you enter a door.
I wonder how much this actually helped the business in the long run, rather than making a lot of people think 'wow these Atari games are buggy'. In fact I wonder how many games available now as abandonware were better at the time because we don't realise they have copyright bugs? Most of the versions of Gunship for the C64 definitely have issues that didn't used to exist.
Emperor of the Fading Suns had a devious method - if you failed or otherwise found a way to by-pass the anti-piracy check, they would let you play the game and it might seem like everything was playing normally, but as you went along it would slowly start subtracting cash from your treasury. The longer you played, the more it would subtract, so by the time you realized what was going on and found yourself mysteriously bankrupt, you had already invested a huge amount of time into the game, which was now guaranteed unwinnable.
I wonder what a TAS of that game with the anti-piracy check triggered would be like, could the TAS beat the game fast enough to mitigate the effects of the anti-piracy?
Some anti piracy bugs would also be good to look at. Like when I bought a brand new copy of red alert back on release day and out of the box it would trip the anti piracy unless you defrag your hard drive repeatedly right before running the installer. I had to call Westwood to complain and thats what they told me to do and it worked everytime.
4:31 Maybe this check is the source of the misconception some pirate groups (particularly in the nes/famicom scene) had that if you remove all copyright information from the game you are safe from the legal standpoint.
Kinda-sorta. Proving reams of machine code are identical would be a challenge for the courts, but having the copied game flash in bright letters, "COPYRIGHT ATARI" makes proving infringement trivial.
I remember seeing the 6502 piracy code while porting/emulating Tempest. I didn't understand exactly what the PoKey check was doing (didn't matter cause the result was ignored). I assumed it was testing RNG but didn't know how this one worked... thanks for explaining that!
I'm surprised these sort of checks and stuff were done back then. But it seems like a clever and multilayered system. You should do a video on the Mac Wars antipiracy system that was only defeated in 2020, more than 30 years after the game's release.
I wonder which one's more common: up front copyright checks that brick the game, or the insidious ones that only show up later. They're both pretty common for their own reasons (and often used together).
If I remember correctly, the first Tempest machines had an incorrect complement value hardcoded in, meaning the anti-piracy measures would kick in even on a genuine machine. There's an article in Joystik magazine September 1983 about the effects based on the last two digits of your score after earning the 188,000 point bonus, including getting 40 free credits!
was playing it in 1981 and we discovered this feature ourselves. It wasn’t a bug IIRC, more of a backdoor coded by a couple of the devs. Make sure your score is at least 180,000 then ensure the last 2 digits of it end in a specific value. Let the game finish then wait for it to loop into demo and high scores screens. On the second loop the glitch would activate - unlimited lives, start at any level, 99 free credits etc. Make sure your score is at least 180,000 then ensure the last 2 digits of it end in a specific value. Let the game finish then wait for it to loop into demo and high scores screens. On the second loop the glitch would activate - unlimited lives, start at any level, 99 free credits etc.
I was playing Tempest in 1981 and we discovered the free game feature ourselves. It wasn’t a bug IIRC, more of a backdoor coded by a couple of the devs. Make sure your score is at least 180,000 then ensure the last 2 digits of it end in a specific value. Let the game finish then wait for it to loop into demo and high scores screens. On the second loop the glitch would activate - unlimited lives, start at any level, 99 free credits etc. Make sure your score is at least 180,000 then ensure the last 2 digits of it end in a specific value. Let the game finish then wait for it to loop into demo and high scores screens. On the second loop the glitch would activate - unlimited lives, start at any level, 99 free credits etc.
I randomly came across this video in my feed and I have to say I'm really impressed with how you presented your video. Usually these topics go over my head but it's explained very well and I learnt a lot! Definitely earned a subscription and I'll be watching more of your videos 😊
Another good checksum method is a dummy file; or data that a copy program would normally ignore; some devious Famicom Disk games used the dummy file method. "There are 13 files on the disk", says the index file. But that's a lie, and there's actually 14.
Some commodore 64 games had intentional bad sectors and unusually specific errors on the floppy. You need a very specific floppy copier to extract a correct image.
@@viscountalpha But of course, nothing was ever a bad as an anti-piracy measure as LensLoc, the physical measure which (while leading to the creation of Escape Velocity) could lock legitimate buyers out of the game.
I wonder if some very carefully crafted TAS would be able to manipulate what instructions were being implemented by triggering this purposefully (assuming that it can be triggered by the TAS itself on an otherwise non-pirated game).
*Reveals that the name of Atari's RNG producing chip is called the "Pokey" Chip. The Five-Year Old in the back of my brain: "You do the hokey-pokey and you turn yourself about. That's what it's all about!"
This technique of shecking the trademark is still being used today, in places you would not expect. Like making sure one piece of hardware only work with hardware of the same company. So you can't use any other part in that device, even if it's not copied, but a completely new design.
I think an interesting video would be one covering all anti-piracy measures in Spyro: Year of The Dragon. It's perhaps one of the first games to really go at people trying to pirate it with multiple checks through the whole game, it erases resources from you as well, but it doesn't crash nor prevent you from playing the game. It just makes it impossible to beat.
4:00 Atari had good reasons for it. The digital piracy prevention was a lot less sophisticated and with these devices being standalone and not networked, there are very little legal ground for them to go after. However, temperament of the trademark can call for immediate legal action. That's why the Gameboy had similar checking to counter both piracy and unlicensed games
the copyright message is probably an excellent vector to enable legal attacks on pirates. Later Nintendo wound up doing something similar with the Gameboy. The lockout code was a tiny bitmap image of Nintendo's own trademarked logo, which is why pirated cartriges were a trademark violation. I suspect in this case, by forcing the pirates to leave the copyright messages intact, they'd legally be "on the hook" for damages.
I recall playing Tempest back in the 80's and there was some "trick" which allowed you to open high levels by getting some score and letting your players die. I don't recall the details though.
Back in the day, I had some gaming disks (5.25 disks) and one had a checksum on resistors in a DIP header on the game port, and another version looked for a certain character at startup that was pressed on the keyboard. If it wasn’t seen, an increment would happen. After about 10 increments if I remember correctly, the whole disk would just stop working. This was stuff I was doing back in the 80’s with Apple computers. Fun stuff! Watching this video brought back memories of the sneaky copyright schemes we could do.
I remember a 3D fighter jet game on the Commodore Amiga, a pirated copy would play for about a minute and the plane would then lose power forcing a literal crash into the ground every time. Back in those days I was a naughty boy, I found the code responsible and disabled it.
@@melissawickersham9912 In those days I showed it off to a few friends, but that was all, it was more of a challenge, I was fascinated how the code worked and I usually made cheats for games even from the Commodore 64, some got in Zzap!64 magazine. Piracy on the Amiga was everywhere, there was even a market stall selling pirated games for not much more than the cost of the disks that didn't get caught, I never did that. The scene was establishing itself with quite a few cracking groups already around (I never became part of anything like that) and there was what you call copy parties where people would turn up with their Amigas and see disk drives lined up copying, one I heard got raided.
Didn't an early official version of Tempest always trigger its anti-piracy code because of a last-minute realignment of one of those copyright notices on-screen? That extra byte could be the fix for that.
want to make a more memorable antipiracy system? make a code that straight up turns the game into a creepypasta melt the graphics. make sound play progressively deeper. add some threatening messages make players so terrified that their pants disintegrate from whatever comes out of their body
Earthbound does that quite well; it has a dozen checksum sets that once tampered with cause vicious backlash from the game engine; it cascades at the final boss where upon swapping to the final boss it swaps your SRAM (Save Data) into an active bank and hammers it front-to-back with a RNG. There's also DKC; notably 2; most emu's mimic the required hardware well enough and once the initial checksums are passed it loads normally and checks region next. If you play through the game there'll be missing items, and some interactions are handled badly resulting in strange interactions between characters. DKC2 also hammers your save data once some antipiracy junk is triggered; I suspect it's to defeat copiers with massive RAM; and can load the SRAM into live data and hammer it with a boatload of RNG calls. It can go further and actively save your broken data, and when the cartridge loads it seems to pull wrong values from somewhere and immediately crashes when it can't load the title screen and copyright screen from Rare. Earthbound makes terrifying noises, DKC2 causes mind-melting alterations to your world as it becomes unstable and melts down under the intense pressure of corruption acid. They're hard to find but some of them are out there with how they handle machine code.
Sweet. That loop off-by-one thing happens a lot more than you’d think. If it doesn’t break anything, no one notices. I was once disassembling the C64 ROM and saw where it initializes sprite colors during a cold reset it goes one address too far. How about that. :)
@@grantofat6438 rewrite Tempest in C++ using the vector layers and write your own graphics engine to render these vector graphics as console characters right now. or, are you, perhaps, too incompetent to do so?
@@grantofat6438Honestly it's not so much incompetence as it is that coding is hard. And tedious. In thousands of lines, you're always going to miss SOMETHING, espcially when your ability to feed yourself and pay your bills depends on getting the product up and running well within a certain time frame.
E5A8 LDX #$2F E5AA LDA $ECB8,X E5AD STA $CFFF,X E5B0 DEX E5B1 BNE $E5AA Interesting! I had to go looking for this code. Here it is. The table at $ECB8 is missing the last byte (presumably 8, "orange") but instead uses 76 (the letter "L" of LOAD) to initialize the last sprite color to medium grey instead. Harmless, but neat. The table of actual values begins at $ECB9 which makes sense because the destination is also off by one.
If the game devs have tightly integrated control of custom chipsets and are writing code at assembler level, I'm actually more impressed with pirates being able to copy a game at all, it seems almost impossible to detect the fairly trivial ways asm code could check that it is running in an expected way.
Checksumming the copyright message made sense back then because the only way to copy it was to put the copyright message (it wasn't but Atari thought it was), and if someone put it, Atari could sue them to hell.
Interestingly, the exact same POKEY RANDOM register read test is done on the 8-bit computer series to detect malfunction/missing POKEY chips, as well as detecting additional chips on the address bus for stereo setup
How does that work? The POKEY chip has 16 registers mapped at D200-D2FF. The way the memory mapped chips worked is that they had just enough address bits for the registers (4 for POKEY's 16 registers) and a chip select line where the motherboard determined if the upper addresses matched the range it was mapped into (D2xx on the 800). That means on a stock Atari, the POKEY's registers are duplicated 16 times. I believe most stereo POKEY add-ons put the first POKEY at D200 and the second at D210 (likely duplicated 8 times instead of 16). This was trivial to implement, as the POKEY has two chip select lines, so one of them can be the added address line. So if you read the RNG on the "second" POKEY on a stock system, you'll still get good RNG values; they'll just be the same as the first POKEY would produce. And presumably they booted on the same clock cycle, so both would likely be producing the exact same values anyway. But for detecting a malfunctioning chip, that would be a valid test.
It's always cool to see the anti-piracy measures implemented by old games. Simple, yet effective to give pirates a hard time when creating bootlegged systems and games.
Pretty clever stuff from atari,especiay back then. BTw i really like your video’s as how they are,no ‘funny’ jokes,no stupid annoying generic parts,no sarcasm,no overdoing attempts of being spontanious,not showing any private situations, no missury,it’s just perfect, Thing is that if i am in for funny jokes,i will go watch commedy,it’s just simple as that.
I didn't figure it out code-wise, I did it with statistics. But check out the C64 version of Steve Jackson's OGRE. It does a disk check for a specific error on the disk that your 1541 cannot create. If it doesn't find it, it shifts the combat tables by 1 in favor of the OGRE. Your 33% chance to hit treads? Just became 17%. The OGRE will win every time. It's diabolical.
Very nice presentation! We had to learn assembly in school. You really had to know the architecture of the CPU and the peripheral hardware. But, it gave you real control and speed when programming.
Checksums are also often used to check if the data has been correpted, in addition to being intentionally tampered with. So in that case the copyright would be acting as a short check for whether the ROM is still functional
I thought all games crashed for antipiracy reasons in order to make it hard for hackers to pass checks. On Bubble bobble arcade, the "original game" cheat is a hardware piracy check also, if it fails it gives the player 100 credits (thus making the arcade cabinet useless for profit reasons) and leads to "DEAD COPY GAME" message, pass leads to "ORIGINAL GAME" message + the cheat.
Xevious was infamous for this as well. when you do the name trick, as long as the checksums pass, you get the "original program by evezoo" message. but if you mess with the game title or copyright, a different message is printed. DEAD COPY. MAKING COPY OF NAMCO PROGRAM. You only thougth you removed het word namco from your bootleg... :) and with this evidence, copyright infringement is proven.
It is such a funny thought. I'm an electrical engineer, but i have more in common with the devs of yore that worked on these games. Than your average programmer does. Cause they too had to know how the processor was interacting with its peripheral circuits. To know exactly how the Interface chips like the POKEY and the C64 CIA operated.
wikipedia: "The Atari 2600's CPU is the MOS Technology 6507, a version of the 6502, running at 1.19 MHz in the 2600." In effect the same as the C64 but with an alternate set of peripheral chips.
i cant get enough of these. your voice is so nice to listen to, it helps me sleep! that and these are interesting as hell so I gotta end up listening to them over and over so they stop being interesting lmfao
That BPL instruction should have been BNE. And the checksum is calculated backwards. This is something that I very often do because DEY sets the Z flag in the status register. If you calculate the checksum forwards, you need a CPY instruction. Doing it backwards allows you to lose that compare instruction, but it does also mean that you have to store your text backwards too if using an offset to print text. Nearly all additions require you to CLC before doing the ADd with Carry. The same as you SEC before doing subtractions. What you are getting wrong when you explain this checksum code is that the Accumulator is 8bits. It never reaches a point where you only look at the lower 8 bits because it's ONLY ever 8bits. Also if you look, the result of the addition is stored in Zero Page which some other code will need to check. That just involves an LDA and BEQ.
Looking at 5:40 in the video, using BPL did no harm except include the X-position into the checksum, just as the LDY #16 caused it to reach one value too far. It exits the loop when Y decrements into the "negatives" (255). This is a good way to include the zeroth item in a list sometimes. You are right, he "shows" the addition happening forwards, when the processor is actually adding last term first. The CLC is only here so the carry flag starts from a known state - the carries that occur along the way have been expected and accounted for in the final check.
A thousand thank yous for this! I just picked up a Tempest board and knew there was copy protection, but thought I was going to have to reverse this stuff for myself. THANK YOU! 👍
Tempest was my absolute favorite video game, bar none!!! On another note, my cousin was married to the late Jerry Logg, father of Ed Logg who created Asteroids :)
I ram into the Pac-Man check when I hacked the pacman ROMs on this channel, to get to the kill screen fast. I always hated the rom checks. But this one Ik tempest is actually sneakier because not gives the illusion it all works.
What if we just draw a black credit over the existing one? The Atari copyright will still be there, but there's just something over it preventing the player from seeing it.
This is a vector-based arcade game, so you're essentially drawing with light. Drawing with "black" is the same as drawing nothing. Though I suppose you could draw a solid rectangle over the text making it unreadable.
That's beautifully evil. I love the old Atari vector machines. There's probably a video's worth of stuff to be done about the pseudo 3d math hardware in the atari mathbox. I have a bunch of documentation on it that I reverse-engineered, drop me a line if you're interested.
It’s tricky and clever, but I wouldn’t call it evil. These developers are trying to defend their software creations against pirates, after all. The legitimate creators and owners of the software are the good guys in this case.
A similar anti piracy method that was used on Spyro the Dragon on the PS1. If the game found it was a pirate copy, it would make later levels impossible to complete. But the hapless pirate would not find out there was a problem until he was a couple of levels in.
Honestly this just makes me wish I had a rotary dial or a real Tempest machine. I love this game so much. So glad to know there's cool anti-piracy stuff in this game too!
I'm currently reverse engineering a H.E.R.O. C64 cartridge image. I'm finding that there are multiple locations where it technically writes break commands to code points in cartridge, but if the cartridge had been dumped to load from disk to RAM, these commands would corrupt the game and cause it to reset or crash.
i find it extremely funny how atari decided that the copyright string _must be displayed at all costs_ and will prevent the game loading otherwise. I know this would prevent most pirates from messing with the game and avoid lawsuits or smth, and yet i still find it funny.
THAT’S how Decimal Mode one the 6502 works‽ It’s so obvious in retrospect but I’ve been perplexed about it’s actual use for a while now- actually makes a lot of sense for the eta.
I read that Nintendo removed the decimal mode for their Family Computer/Entertainment System just to dodge the patent, so that's the one thing NES coders may not have any experience with!
Back then protection did work again piracy as there was no emulators and you need to buy hardware with the game or physical roms either way, they been againts bootleging and unlicenced use of hardware, for that all you needed was to force to use tradmarked logo or copyright to boot the hardware, so hardware force you to illegally (or else you got legal licence) use trademarks and they can chase you for that. Consoles used that too and used logos as a key to boot the game and display it on screen, most known example Game Boy or PlayStation 2
Using the player's continuously changing score to quietly crop-dust the game's own code with errors is just beautiful in its elegant malice.
I know it's kind of hilarious that instead of failing in a constant way, it fails in a way dependent on what's in the game's memory.
Atari essentially did what the modern “realtime corruption” tools do, but way before those would exist!
I'm suspicious that in development they had some memory corruption bugs (which of course they fixed), and they decided to force the same bugs with the piracy detection.
@@pfcrow No way, this is 100% intentional. Using the low byte of the player score is a cheap source of randomness. All of these tricks are designed to be difficult to debug, and I take my hat off to the elegant malevolence of their author.
I once had to solve a similar problem of building a cheater-detection algorithm in a javascript game where it would be trivial for lots of people to inspect the minified-then-reexpanded source code. It was similar because all of my mechanisms would be in code that my opponent could freely read and inspect, so security through obscurity is the name of the game. In my case, the cheater's modified code would be sending a fraudulent game state to a server where it would then become visible to the honest players. I figured most cheaters would try to hack the bytes being sent to the server without tracing all the way through the code to find their origination, so as deep as possible down the stack I computed a checksum of the game state and stored it in the nanoseconds digits of a timestamp that existed primarily to serve this purpose. A user could then hack the score report being sent to the server, and it would seem to work, to them, but unbeknownst to them the checksum mismatch would be detected on the server and their account would be segregated into a "cheaters only" pool where their bad behavior couldn't discourage honest users. It might take them some time to figure out that their account had been poisoned, at which point they'd had no idea how it happened. And debugging it would require constantly generating new user accounts. It could be done, but would take a rare level of dedication.
Point is, you want to separate the method from the action, such that the code doing the check lays a landmine that doesn't explode until later so that when the black-hat debugs into the problem, there are no obvious hints as to how and why the bad state came to be. They then have to run the code again watching for changes to a memory address, but maybe the next time the landmine is laid elsewhere. You might have to build special-purpose debug tooling to ever figure it out.
Although with arcade games, it really feels like punishing the player, who just came into the arcade and tossed in a quarter, when they would have had nothing to do with the pirating.
All the while, who ever put together the counterfeit cabinet or sold the board to put into a bare one, still made money on it, so these tactics likely didn't do anything to stop those actual pirates.
So like with more modern DRM from recent decades, it's end users who give their money to play who get screwed by the game's maker (and/or publisher.)
Edit: typo
The anti-piracy game corruption techniques are honestly hilarious. I love the little devious methods old school software used.
Similar anti-piracy techniques were used in Spyro 3: Year of the Dragon.
@@imveryangryitsnotbutter What they did was essentially screw up your save as time went on.
And the same thing is done in Earthbound on SNES.
However, that game also resets all your progress when you go to the final boss.
@@pacomatic9833Year of the Dragon also resets you at the final boss
Megaman X has a system similar, resets, restart level, etc.
These "slow pirates down so much that people early on are just going to buy the dang game" are so cool. It's sad that they've fallen out of fashion but... that's also literally what modern anti-piracy does. Denuvo is possible to crack, but it takes weeks for the One Person Who's Capable Of It to manage it-if you follow modern games and piracy, you'll notice that most of the hype around a new game will have died down before cracked copies are available. When a lot of modern games live or die on their first week of sales, just stopping people pirating for a fortnight makes a ton of difference.
Denuvo just does it with complicated and weird maths, rather than making the game slowly fuck up as time goes on , but the impact to pirates and consumers of pirated games is the same.
one reason why they likely bound the checksum to the copyright notice specifically is that it gives them an extra legal avenue to pursue in that they aren’t just altering the code to work, they would have to fraudulently misrepresent something with altered copyright information as that’s the only valid set of values. that’s why for example, the sega genesis would display ’licensed by sega’ etc, because an unlicensed game would cause that message to display and essentially become a legal claim. there were some interesting court cases around this, and i imagine the copyright notice here being the checksum serves a similar function.
Nintendo tried something similar with the GameBoy, since the logo is loaded off from the Cartridge, and displayed on the screen.
If the logo shows up correctly, a check passes and it boots up normally, if it doesn't, it doesn't boot.
However, pirates found out how to bypass the check by changing the values the check sees compared to the ones being displayed, so if you see any Cartridge displaying a logo other than Nintendo's and still booting up, now you know why.
I remember that Sega's implementation was tested in a court. The affected party claimed that the licensing message was just a techical requirement to get games to work and not actual violation of the trademark, and the court agreed. But this happened years after Tempest was released.
Yep, that’s Sega v. Accolade case from ’92.
However, in this situation this wouldn’t work the same way since there is no hardware or firmware check that the copyright notice exists. It’s likely more so that it’s hard to remove the notice and having the notice makes it simple to notice and prove that the code was copied.
Makes sense, iirc back in the 80s legal protection for software was pretty much nonexistent so relying on the "classic" copyright laws was probably the only way to get some protection at all.
@@mina86 true. absolutely not a 1 for 1. i just imagine if atari sniffed out an arcade or distributor or whatever 'altered attribution' or something it could be an extra thing to tack on. it would make it harder to plead ignorance at any rate.
The checksum mattered to ATARI because pirates would remove copyright messages, allowing arcade owners and bootleg manifacturers to go "but I didn't know" by "forcing" copyright messages, ATARI could then point to the copyright notice, and claim that they had to know, they were told on the title screen.
Interesting
Yes, it's quite funny though. You can do whatever you want with the game, so long as you buy their hardware and keep their copyright.
@@flameofthephoenix8395 Doing what you want with your own game is one thing. Bootlegging is another.
@@MRMIdAS2k I wasn't saying that you should take part in bootlegging.
Also, it means even if you have a bootleg Tempest cabinet in your arcade, it still shows Atari's name to everyone in the arcade, including anyone who sees the game and decides they want to buy it for *their* arcade, so Atari still has a shot at getting some sales out of it.
One fun thing about the graphical glitches, if displayed on a real machine there is a chance the monitor will be damaged. WG K6100s are pretty delicate, if the deflection input is out of range (ie drawing shit outside of the normal bounds of the screen) it can cause too much current to flow through the transistors that drive the yoke, causing them to short, blowing out the voltage regulator transistors and causing you to have a very sad monitor. Almost anyone who has or had a color vector atari machine knows the pain. They're pretty annoying to repair.
That means that the bootlegger removing the copyright message could end up having to pay more than they earn with the arcade money.
Ah yes, The Pokey Chip. Right there next to the Shadow Chip, the Speedy Chip, and the Bashful Chip.
the pokey chip, the neighbor to the opposite ness chip
who of course, lives with his brother, papyrus!
With how formal and instructive your videos always are, that little "...apparently" caught me off guard, I probably laughed much harder than I should have
Timestamp?
@@TH-vo6hv 4:05 is the start of the sentence
I once went to an arcade, it’s probably been five years since this happened, but it was one of those typical “we put smartphone games on a bigger screen and called it a day” type of arcades. Yet, for some reason, literally sitting UNDER a set of stairs, there was a Tempest machine. You know damn well what ensued afterwards. Best arcade I’ve ever been to, not that that’s saying much, since most of them don’t even have anything besides the aforementioned smartphone games, and I haven’t been to all that many.
(By the way, this wasn’t some reproduction or an emulator in a box. It was a genuine musty old piece of work, and why it was in this place, I have no clue.)
I hate those giant smartphone games. I went back to an arcade of my youth expecting to see the faithful old HOTD 4 and Mario Kart Arcade GP 2 machines and there they were. It hurt.
gotta love the random tempest machine
"oh"
"Thats a tempest machine."
"theres a tempest machine in an arcade full of shitty mobile games."
I remember during a behind the scene video about Tempest, there was a glitch/failsafe that if the copyright wasn't in a specific place, the game would automatically add a large number of free credits. this kept machine owners/renters form using unlicensed products.
I think I've heard the same thing about Asteroids. Though, that one also had a "trick" where people would get down to a single small asteroid and spawn-camp the small ships, racking up insane points and lives. Enough to be able to take a bathroom break during marathon sessions, for instance. Arcade owners didn't like that, since they were playing on a single quarter.
@@TyphinHoofbun - i remember this trick although I never could do well in Asteroids although Atari came out with a revised ROM to solve for this issue
@TyphinHoofbun That's easily solved by limiting extra lives, either total or per stage. Later games did.
Tempest has a brilliant hidden feature in the v1 and 1.1 versions of the game back in 81. I stumbled across it while playing it in the arcade then never spent more than a quarter ever playing it from then on. You ensure that the last two digits of your score ended with a specific value, then let the game and go back to demo mode. At the second loop of demo mode the game would then react depending on the digits. 99 free games, ability to start at any level, unlimited deaths etc. It was intentional - a thank you to us obsessive players.
@@pokerpig9069 How do you figure this out without being able to see the code?
It is interesting that if the game's software or hardware is modified, you will still have a free trial, but then the game breaks completely after the trial ends.
It makes it harder to be sure that you've really cracked it correctly this time.
By putting antipiracy checks at difficult levels, they all but guarantee that the pirates who are good at messing around with the code but likely not experienced Tempest players, won't trigger it. Then they get the joy of deploying a bunch of these clone cabinets and then the complaints pour in from arcade owners when players keep complaining that the machines are crashing.
This would be far less of a nuisance if the pirates knew there was a problem before they manufactured and sold a bunch of these things.
This was rather interesting. Years ago I was quite heavily involved involved with software and hardware development on PCs. One anti piracy technique I developed was based on floppy disk storage. The way data is normally stored on disk is as a series of Sectors on each track. Each sector is numbered but generally, not (as you might expect) in order. Instead, the sectors were arranged so that, after reading the sector No 1, you'd skip the next and then the sector after that would be Sector No. 2. This would give the bios time to be able to process the first sector before reading the second. After a complete rotation of the disk, you'd then have half of the sectors on that track. A second revolution would follow the same pattern but reading the alternate sectors that had been skipped on the first revolution. So it would take two complete revolutions of the disk to read one complete track. This was actually faster than having the sectors in order because if the bios missed the beginning of just one sector, it would have to wait a full revolution of the disk to get back to the missed sector. Having an intervening sector made this less likely to happen.
Now for my anti piracy method, I'd run a custom low level format on the disk, such that one track (eg. track 7) had all the sectors stored in reverse order. This made the time to read that track take much longer to read than any other track. (typically 16 revolutions of the disk compared to 2). Once the disk had been put through this low level format, it could be written to in the normal fashion but when reading that track, it would take 8 times as long to read, compared to the other tracks on the disk.
If anyone ever used standard tools to copy the disk, all the data would be perfectly copied over BUT, when reading that track, it would read at the same speed as any other track. Thus giving away that it was not an original copy. The beauty of this was that the client could even format the original disk (using the dos Format command) and download an updated version of the software and write it to the disk and it would still work. (formatting doesn't overwrite the low level format, it uses the existing sector markers). So effectively, there was nothing to see in the software, it was the disk itself that had been "marked" as authentic.
I used some similar methods on CDs and obviously we had other techniques at our disposal. I was asked to implement a process that would copy the serial number of the CPU onto the floppy disk on first setup to bind the software to that one machine, but I refused to implement that, as I felt, if someone has paid for a copy of the software, they should be allowed to upgrade their machine without loosing functionality of our software.
Same but I'm not gay
@@Amberlynn_Reid Lol, and I'm not a pirate 🤣😂😁
Lots of Apple II titles also did wonky things to the on-disk format (resizing sectors, changing required spindle speeds for specific tracks, etc.) so as to make it more difficult to produce working copies even if you had the binaries. The Apple didn't have a "smart" disk controller and did everything in software with the CPU, so it was possible to make the drive physically do all kinds of weird things to accommodate non-standard protected disk formats.
This is fascinating
@@stevepreskitt283 I also used to write the BIOS routines to access disk drives. One of the easter eggs I put into one of our bios chips allowed you to play a tune on the floppy drive. It was quite a crude routine that just drove the head stepper motor at the required frequencies. This was discovered by my boss when he asked me "Why is my floppy drive playing La Marseillaise?" I then informed him "That's odd, it should be playing the intro to All You Need Is Love"
Wow, this is absolutely diabolical! As a kid I used to crack 8-bit computer software, and once the idea of delayed validation occurred to me, it was always in the back of my mind. I only ever found one case, though - a cartridge game that clobbered itself with garbage at random intervals to thwart RAM-based execution. I think this sort of thing was rare because protection was usually bolted on by the publisher rather than baked in by the developer. Anyway, thanks for the amazing video!
I would assume that the reason the checksum only checks the atari copyright text is so that anyone who makes an illegitimate copy of the game can be sued on the grounds of copyright infringement, similar to how nintendo used their logo for legal copy protection for the gameboy.
I assume you mean trademark infringement. Making an illegal copy is already copyright infringement regardless of if the logo is there or not.
The Gameboy case was interesting, but was designed to prevent unlicensed games rather than piracy.
The logo WAS the key, so there was no obvious way to make a compatible game without displaying the Nintendo logo and committing trademark infringement. One company ultimately designed a cartridge that switched memory banks so the real logo would be read for the check and there's would be read for the display, even though the GameBoy thought it was reading from the same location.
Nintendo tried to sue them for copyright infringement for even having their logo data in their code, but the game maker won because the only way to make a compatible product was to include that data. It would be like Microsoft suing you for including PE headers in your program
@@charlesnathansmithnintendo was SO CLOSE of doing it perfectly and they f'd up the smallest detail and made their efforts useless
@@niko5008 it does add a significant amount of complexity to the cartridge though, which increases any unlicensed games cost due to both more expensive cartridge hardware and r&d costs
@@sircalvin they could just put some RAM in the gameboy that save the logo so they can be read twice with no problems. Or maybe just check the ROM and write it in the vram at the same time so it can't be bank-switched so easily.
Finally, an actual anti-piracy screen
True
I really wouldn't mind all the fake ones if the uploaders didn't pretend they are real.
Every copy of Tempest is personalized
That meme is kinda annoying since it makes it harder to find information on real anti-piracy stuff.
...and that means the rest of "anti-piracy screens" in videogames are fake as some type of videos showing false and not accurate "anti-piracy screens" which most of them are maded with modern hardware and software, most common video editors, image editors or music production software for try to recreate it?
I mean, although the Tempest one it's really impressive for a game I don't know games with methods almost comparable or superior, if you want some real anti-piracy screens check out most of the classical "Error: Pirated copy" text or something in a plain background.
I love these types of videos. Do you think you could take a look at how Earthbound anti-piracy measures work? It has a pretty devious payload of wiping save data. It also shows some random corrupted visuals and sound effects that seem to be different every time, so I've always been curious about how exactly it works.
turning on decimal arithmetic is hilarious, that's my favorite one! 😆 I also really like the hardware RNG function in general, making crappy RNG values but doing it really frickin fast so it's good enough to work. I haven't researched this era of games very much so i never saw that before, i'm more used to NES/SNES RNG where it's in software.
Spyro 3 also famously has a bunch of individual anti-piracy checks that are triggered at different points in the game to make it frustrating for hackers to bypass them, making the game just slowly get less playable over time. I don't recall the exact method used for the checks though, but there's probably a dozen videos about it.
pseudo rng is still the most common. True random numbers are generated by non-deterministic things which circuits are incapable of. Id look at tom scott’s lava lamp that keeps the internet safe video
I think the x86 instruction set has a real RNG instruction, but it also takes many cycles.
Yeah, I've heard of Spyro 3's anti-piracy measures, and Mother 2/EarthBound's anti-piracy measures are really interesting too. If I remember right, when making a new save file, the game checks the amount of RAM on the cartridge, and if the RAM amount is incorrect _(because bootleg carts usually have more RAM than legit carts),_ it makes the enemy spawn rate EXTREMELY high and also places enemies in locations that don't normally have enemies _(e.g. Onett after beating Frank),_ causing EarthBound to become nearly unplayable.
Oh yeah and it also crashes and deletes all of your save files if you manage to make it to Giygas
It was a common practice for bootleggers to alter or erase copyright strings in games. I remember reading on TCRF the ways Konami would put anti-piracy checks in their late-gen NES games and the way they'd mess with the player if they were tripped, such as making Super Shredder invincible in TMNT3 so you couldn't beat the game. In all those cases, it was the removal of the word Konami that triggered the check, so what Atari did for Tempest is not that unusual.
And then Russian kids would be wondering in frustration why can't they beat Shredder when they bought the game from Steepler on a licensed Dendy cartridge.
Similarly for cracks of home videogames, the crack group would put their names and greets to other crack groups in the game (this eventually became the demoscene). While any half decent cracker would just remove these checks, you would assume the theory was to catch crackers out when they gloated about cracking the software.
Atari had a thing for linear feedback shift registers. They used them to create gritty audio waveforms as well.
It isn't just Atari. That's how most pseudo random number generators, both hardware and software, work.
LFSR was used by David Crane who wrote the game Pitfall to generate random yet repeatable scenes/pages within a game when moving left or right. It was mainly done for saving memory in those early machines, rather than drawing out each scene/page individually. It was quite clever and worked great. ;)
For anyone wondering why the copyright string is so specifically protected, it was common practice in the day for bootleg arcade machines to alter the data, which at the very least would generally include a different title and copyright string. Essentially this was done in the hope that they could technically say, for example, "we weren't distributing unauthorized copies of Mario Bros, this is _Pest Place!"_
Because game mechanics in itself are not copyrightable. For good reason, it would stifle creativity dramatically to allow such protection.
@@silkwesir1444you can get a patent on some of them 😐
@@silkwesir1444 That was the logic that game bootleggers were attempting to make it look like their "products" fell under. However, the fact remains that the _code_ is still proprietary, and bootlegs still lift the code without permission, no matter how much the branding is dolled-up to look different (as opposed to clones, which are clean recreations of the mechanics without stealing the code).
Never did I think a video about some random arcade game’s anti piracy would captivate me for 30 minutes.
The visuals were astonishing and easy to understand!
Honestly games just messing with you instead of just stopping you from playing at all is my favorite type of this
Earthbound also did this where enemy spawns get greatly increased and the final boss crashes the game and resets your save before you can beat it
Tempest is one of my favorite arcade games and I NEVER knew that it had any piracy checks. Nice job!
At the time memory was expensive and limited, I wouldn't have thought they could afford to waste memory for piracy checks.
Which is exactly how good anti piracy checks /should/ work. If everything's legit, it shouldn't be detectable.
The piracy check definitively is interesting with the side effect it also caught emulators and is almost like an accidental forethought of anti-emulation like performing a division on the SNES when the result is not ready (which would trigger ZSNES, an emulator infamously known for its inaccuracy like instant arithmetics).
The last phrase when you mentioned your supporters also is a very good point given that DRM measures are bound to be broken and thus mainly focus on the release (where the hype is typically the largest) and coding knowledge of the game is naturally the smallest for any outsider.
The software protection also made me realise that according to some Discord messages or UA-cam comments, pirated SNES games often are dumped on cartridges which have more than enough to not deal with not having enough RAM which in turn also has been used for anti-piracy measures by taking advantage of mirroring.
As a realistic example, a game comes with 8KiB ($2000 bytes or the mapped address range $0000-$1FFF) of cartridge RAM stores some value at $1FF0 and then a different value at $7FF0 (which is valid for 32 KiB or $8000 bytes of memory / has the range $0000-$7FFF). By mirroring, $7FF0 is reduced to $1FF0 (because $7FF0 & $1FFF or $7FF0 % $2000 = $1FF0) on the 8 KiB cartridge. It then compares the latter value with the one of $1FF0 and if both are unequal, it means the game has more RAM than it's intended and thus must be pirated.
Super Mario 64 not crashing on officially emulated rereleases when the camera enters a parallel universe is also this. The Wii/U/Switch uses its own FPU rather than emulating the N64's; and their FPUs don't have the glitch that causes the crash.
Few if any SNES games actually used division and multiplication for this check. IIRC Byuu himself mentioned that BSNES doesn't use it by default because it's inconsequential in practice when dealing with official games.
@@fungo6631 That's why I mentioned "accidental forethought" (or rather, accidental futureproofing") in the OP because most pirates used physical cartridges and original hardware while emulators became important only later on.
It's also very much a thing in BSNES to accurately calculate mult/div with at least the version I use so the information you have are likely outdated.
Mess with our game? Sure
Mess with our name? Absolutely not
@bensmith3890The GBC only checked the top half of the logo, as well. Also, there were some clever workarounds based on the fact it was loaded into vram and then checked afterward, meaning that if you supplied your own logo for the first one and then swapped it back to the Nintendo logo for the second one it'd still boot properly while showing something different onscreen.
Donkey Kong makes sure the "INTEND" in the Nintendo copyright is unmodified every time a barrel object is destroyed, if it is modified it'll freeze
Would any pirate leave the copyright information intact? I doubt they'd want to advertise that they are ripping off the owners. So of course they will get rid of it,
It's a legal cover-your-own-ass move, iirc. Sharing pirated games or romhacks was a legal grey area back then, but copyright infringement is *not* so legally grey. It gave atari a much easier avenue to go after pirates.
Final Fantasy 1 does a similar check on the programmer's name on the title screen. It's much more obvious though; the game just freezes when you enter a door.
I wonder how much this actually helped the business in the long run, rather than making a lot of people think 'wow these Atari games are buggy'.
In fact I wonder how many games available now as abandonware were better at the time because we don't realise they have copyright bugs? Most of the versions of Gunship for the C64 definitely have issues that didn't used to exist.
The amount of sass and spite in this protection is unparalleled. Love it.
Seeing that 6502 code brings back memories of the C64 era, and I have to admire the ingenuity of the POKEY rng-check - great video!
Emperor of the Fading Suns had a devious method - if you failed or otherwise found a way to by-pass the anti-piracy check, they would let you play the game and it might seem like everything was playing normally, but as you went along it would slowly start subtracting cash from your treasury. The longer you played, the more it would subtract, so by the time you realized what was going on and found yourself mysteriously bankrupt, you had already invested a huge amount of time into the game, which was now guaranteed unwinnable.
I wonder what a TAS of that game with the anti-piracy check triggered would be like, could the TAS beat the game fast enough to mitigate the effects of the anti-piracy?
Turning on decimal mode is a delightfully simple way to break the game.
Just "You know what, f*ck you."
*_Unhexidecimals your functions_*
4:07 Usually pirates remove the copyright information on the title screen so it is perfect for a check.
Some anti piracy bugs would also be good to look at. Like when I bought a brand new copy of red alert back on release day and out of the box it would trip the anti piracy unless you defrag your hard drive repeatedly right before running the installer. I had to call Westwood to complain and thats what they told me to do and it worked everytime.
4:31 Maybe this check is the source of the misconception some pirate groups (particularly in the nes/famicom scene) had that if you remove all copyright information from the game you are safe from the legal standpoint.
Kinda-sorta. Proving reams of machine code are identical would be a challenge for the courts, but having the copied game flash in bright letters, "COPYRIGHT ATARI" makes proving infringement trivial.
I remember seeing the 6502 piracy code while porting/emulating Tempest. I didn't understand exactly what the PoKey check was doing (didn't matter cause the result was ignored). I assumed it was testing RNG but didn't know how this one worked... thanks for explaining that!
Great video and great explanation of truly ingenious piracy checking. Hats off to Dave Theurer, Tempest's designer and programmer.
I'm surprised these sort of checks and stuff were done back then. But it seems like a clever and multilayered system.
You should do a video on the Mac Wars antipiracy system that was only defeated in 2020, more than 30 years after the game's release.
I wonder which one's more common: up front copyright checks that brick the game, or the insidious ones that only show up later. They're both pretty common for their own reasons (and often used together).
If I remember correctly, the first Tempest machines had an incorrect complement value hardcoded in, meaning the anti-piracy measures would kick in even on a genuine machine. There's an article in Joystik magazine September 1983 about the effects based on the last two digits of your score after earning the 188,000 point bonus, including getting 40 free credits!
was playing it in 1981 and we discovered this feature ourselves. It wasn’t a bug IIRC, more of a backdoor coded by a couple of the devs.
Make sure your score is at least 180,000 then ensure the last 2 digits of it end in a specific value. Let the game finish then wait for it to loop into demo and high scores screens. On the second loop the glitch would activate - unlimited lives, start at any level, 99 free credits etc.
Make sure your score is at least 180,000 then ensure the last 2 digits of it end in a specific value. Let the game finish then wait for it to loop into demo and high scores screens. On the second loop the glitch would activate - unlimited lives, start at any level, 99 free credits etc.
I was playing Tempest in 1981 and we discovered the free game feature ourselves. It wasn’t a bug IIRC, more of a backdoor coded by a couple of the devs.
Make sure your score is at least 180,000 then ensure the last 2 digits of it end in a specific value. Let the game finish then wait for it to loop into demo and high scores screens. On the second loop the glitch would activate - unlimited lives, start at any level, 99 free credits etc.
Make sure your score is at least 180,000 then ensure the last 2 digits of it end in a specific value. Let the game finish then wait for it to loop into demo and high scores screens. On the second loop the glitch would activate - unlimited lives, start at any level, 99 free credits etc.
@@pokerpig9069Clever backdoor coding. Those sneaky developers always have clever tricks up their sleeves.
I randomly came across this video in my feed and I have to say I'm really impressed with how you presented your video. Usually these topics go over my head but it's explained very well and I learnt a lot! Definitely earned a subscription and I'll be watching more of your videos 😊
Another good checksum method is a dummy file; or data that a copy program would normally ignore; some devious Famicom Disk games used the dummy file method.
"There are 13 files on the disk", says the index file. But that's a lie, and there's actually 14.
Some commodore 64 games had intentional bad sectors and unusually specific errors on the floppy. You need a very specific floppy copier to extract a correct image.
@@viscountalpha But of course, nothing was ever a bad as an anti-piracy measure as LensLoc, the physical measure which (while leading to the creation of Escape Velocity) could lock legitimate buyers out of the game.
I wonder if some very carefully crafted TAS would be able to manipulate what instructions were being implemented by triggering this purposefully (assuming that it can be triggered by the TAS itself on an otherwise non-pirated game).
If the emulator's working properly, you would need a romhack.
@@KopperNeoman I wonder if an ACE could be found that specifically forces the checksums to fail by writing where it's never meant to.
*Reveals that the name of Atari's RNG producing chip is called the "Pokey" Chip.
The Five-Year Old in the back of my brain: "You do the hokey-pokey and you turn yourself about. That's what it's all about!"
I'd like to see more videos about piracy checks for different games, this one on Tempest was very informative.
I doubt there are that many that aren't just a simple error screen at boot. Or at least arcade games.
This technique of shecking the trademark is still being used today, in places you would not expect. Like making sure one piece of hardware only work with hardware of the same company. So you can't use any other part in that device, even if it's not copied, but a completely new design.
I think an interesting video would be one covering all anti-piracy measures in Spyro: Year of The Dragon. It's perhaps one of the first games to really go at people trying to pirate it with multiple checks through the whole game, it erases resources from you as well, but it doesn't crash nor prevent you from playing the game. It just makes it impossible to beat.
Didn't Earthbound basically do the same thing?
@@KitsuneYojimbo No. What Earthbound does is it lets you play the game until the cave of the past, then crashes there and erases your save.
4:00 Atari had good reasons for it.
The digital piracy prevention was a lot less sophisticated and with these devices being standalone and not networked, there are very little legal ground for them to go after. However, temperament of the trademark can call for immediate legal action. That's why the Gameboy had similar checking to counter both piracy and unlicensed games
the copyright message is probably an excellent vector to enable legal attacks on pirates. Later Nintendo wound up doing something similar with the Gameboy. The lockout code was a tiny bitmap image of Nintendo's own trademarked logo, which is why pirated cartriges were a trademark violation.
I suspect in this case, by forcing the pirates to leave the copyright messages intact, they'd legally be "on the hook" for damages.
I recall playing Tempest back in the 80's and there was some "trick" which allowed you to open high levels by getting some score and letting your players die. I don't recall the details though.
This was great! Very cheeky to show "LSR #4" and "ASL #4" instead of the four each of "LSR" and "ASL", though. Made me doubt myself for a moment.
Back in the day, I had some gaming disks (5.25 disks) and one had a checksum on resistors in a DIP header on the game port, and another version looked for a certain character at startup that was pressed on the keyboard. If it wasn’t seen, an increment would happen. After about 10 increments if I remember correctly, the whole disk would just stop working. This was stuff I was doing back in the 80’s with Apple computers. Fun stuff! Watching this video brought back memories of the sneaky copyright schemes we could do.
I remember a 3D fighter jet game on the Commodore Amiga, a pirated copy would play for about a minute and the plane would then lose power forcing a literal crash into the ground every time. Back in those days I was a naughty boy, I found the code responsible and disabled it.
That *is* a truly naughty hacker move. Were you caught? Or did you get away with it? Did you show it off to your friends afterwards?
@@melissawickersham9912 In those days I showed it off to a few friends, but that was all, it was more of a challenge, I was fascinated how the code worked and I usually made cheats for games even from the Commodore 64, some got in Zzap!64 magazine. Piracy on the Amiga was everywhere, there was even a market stall selling pirated games for not much more than the cost of the disks that didn't get caught, I never did that. The scene was establishing itself with quite a few cracking groups already around (I never became part of anything like that) and there was what you call copy parties where people would turn up with their Amigas and see disk drives lined up copying, one I heard got raided.
Didn't an early official version of Tempest always trigger its anti-piracy code because of a last-minute realignment of one of those copyright notices on-screen? That extra byte could be the fix for that.
Great video as usual, thank you.
Extra appreciation for making the animations look like an Atari vector game!
I haven't written a byte of 6502 machine code in forty years yet for some reason I still know every op code.
want to make a more memorable antipiracy system? make a code that straight up turns the game into a creepypasta
melt the graphics. make sound play progressively deeper. add some threatening messages
make players so terrified that their pants disintegrate from whatever comes out of their body
Earthbound does that quite well; it has a dozen checksum sets that once tampered with cause vicious backlash from the game engine; it cascades at the final boss where upon swapping to the final boss it swaps your SRAM (Save Data) into an active bank and hammers it front-to-back with a RNG.
There's also DKC; notably 2; most emu's mimic the required hardware well enough and once the initial checksums are passed it loads normally and checks region next. If you play through the game there'll be missing items, and some interactions are handled badly resulting in strange interactions between characters. DKC2 also hammers your save data once some antipiracy junk is triggered; I suspect it's to defeat copiers with massive RAM; and can load the SRAM into live data and hammer it with a boatload of RNG calls. It can go further and actively save your broken data, and when the cartridge loads it seems to pull wrong values from somewhere and immediately crashes when it can't load the title screen and copyright screen from Rare.
Earthbound makes terrifying noises, DKC2 causes mind-melting alterations to your world as it becomes unstable and melts down under the intense pressure of corruption acid. They're hard to find but some of them are out there with how they handle machine code.
Sweet. That loop off-by-one thing happens a lot more than you’d think. If it doesn’t break anything, no one notices. I was once disassembling the C64 ROM and saw where it initializes sprite colors during a cold reset it goes one address too far. How about that. :)
Incompetent programmers.
@@grantofat6438Rewrite the entire C64 Kernal right now
@@grantofat6438 rewrite Tempest in C++ using the vector layers and write your own graphics engine to render these vector graphics as console characters right now. or, are you, perhaps, too incompetent to do so?
@@grantofat6438Honestly it's not so much incompetence as it is that coding is hard. And tedious. In thousands of lines, you're always going to miss SOMETHING, espcially when your ability to feed yourself and pay your bills depends on getting the product up and running well within a certain time frame.
E5A8 LDX #$2F
E5AA LDA $ECB8,X
E5AD STA $CFFF,X
E5B0 DEX
E5B1 BNE $E5AA
Interesting! I had to go looking for this code. Here it is. The table at $ECB8 is missing the last byte (presumably 8, "orange") but instead uses 76 (the letter "L" of LOAD) to initialize the last sprite color to medium grey instead. Harmless, but neat. The table of actual values begins at $ECB9 which makes sense because the destination is also off by one.
"Make the game tear itself apart" is a new anti-piracy measure I am happy to be exposed to. Absolutely hilarious.
Spyro on the PS1 does this I think
It would be funny if modern drms did this. You know, the purposeful corruption
Me: This is confusing, I can't understand it
RGME: More?
Me: Please
I'm nearly finished with my Programming 2 course in college and can juuuuust barely understand it. 😆
If the game devs have tightly integrated control of custom chipsets and are writing code at assembler level, I'm actually more impressed with pirates being able to copy a game at all, it seems almost impossible to detect the fairly trivial ways asm code could check that it is running in an expected way.
Checksumming the copyright message made sense back then because the only way to copy it was to put the copyright message (it wasn't but Atari thought it was), and if someone put it, Atari could sue them to hell.
What?
I can't sleep. I'm watching this out of shear fascination and boredom. Your calming voice and simple explanations are wonderful. Thank you.
New videos from Displaced Gamers and Retro Game Mechanics Explained on the same day? There is a Santa Clause!
Interestingly, the exact same POKEY RANDOM register read test is done on the 8-bit computer series to detect malfunction/missing POKEY chips, as well as detecting additional chips on the address bus for stereo setup
How does that work? The POKEY chip has 16 registers mapped at D200-D2FF. The way the memory mapped chips worked is that they had just enough address bits for the registers (4 for POKEY's 16 registers) and a chip select line where the motherboard determined if the upper addresses matched the range it was mapped into (D2xx on the 800). That means on a stock Atari, the POKEY's registers are duplicated 16 times. I believe most stereo POKEY add-ons put the first POKEY at D200 and the second at D210 (likely duplicated 8 times instead of 16). This was trivial to implement, as the POKEY has two chip select lines, so one of them can be the added address line.
So if you read the RNG on the "second" POKEY on a stock system, you'll still get good RNG values; they'll just be the same as the first POKEY would produce. And presumably they booted on the same clock cycle, so both would likely be producing the exact same values anyway.
But for detecting a malfunctioning chip, that would be a valid test.
Thanks for having extensive subtitles on your videos, I could literally read this one at the beach with a limited internet connection.
i am not a tech guy, but you explain this all in a way i can follow and enjoy, real master of your craft
Seems like a crapton of technical overhead just to check for piracy. Excellent video!
It's always cool to see the anti-piracy measures implemented by old games. Simple, yet effective to give pirates a hard time when creating bootlegged systems and games.
Pretty clever stuff from atari,especiay back then.
BTw i really like your video’s as how they are,no ‘funny’ jokes,no stupid annoying generic parts,no sarcasm,no overdoing attempts of being spontanious,not showing any private situations, no missury,it’s just perfect,
Thing is that if i am in for funny jokes,i will go watch commedy,it’s just simple as that.
I didn't figure it out code-wise, I did it with statistics. But check out the C64 version of Steve Jackson's OGRE. It does a disk check for a specific error on the disk that your 1541 cannot create. If it doesn't find it, it shifts the combat tables by 1 in favor of the OGRE. Your 33% chance to hit treads? Just became 17%. The OGRE will win every time. It's diabolical.
That POKEY check right there. That’s so smart, I might as well add an LFSR into my CPU design.
Very nice presentation!
We had to learn assembly in school. You really had to know the architecture of the CPU and the peripheral hardware. But, it gave you real control and speed when programming.
Checksums are also often used to check if the data has been correpted, in addition to being intentionally tampered with. So in that case the copyright would be acting as a short check for whether the ROM is still functional
Always love to watch, even though it can go over my head! Keep it up!
I thought all games crashed for antipiracy reasons in order to make it hard for hackers to pass checks. On Bubble bobble arcade, the "original game" cheat is a hardware piracy check also, if it fails it gives the player 100 credits (thus making the arcade cabinet useless for profit reasons) and leads to "DEAD COPY GAME" message, pass leads to "ORIGINAL GAME" message + the cheat.
Xevious was infamous for this as well. when you do the name trick, as long as the checksums pass, you get the "original program by evezoo" message. but if you mess with the game title or copyright, a different message is printed.
DEAD COPY.
MAKING COPY OF NAMCO PROGRAM.
You only thougth you removed het word namco from your bootleg... :)
and with this evidence, copyright infringement is proven.
this is great, would LOVE to see more anti-piracy routine breakdowns, a ton of games have done this and many have done so in hilarious ways.
I learned of some of these arcade methods just the other day from poking around the MAME website.
My internet dropped out at 0:29 and I sat for like 10 seconds thinking it was part of the video
It is such a funny thought. I'm an electrical engineer, but i have more in common with the devs of yore that worked on these games. Than your average programmer does.
Cause they too had to know how the processor was interacting with its peripheral circuits. To know exactly how the Interface chips like the POKEY and the C64 CIA operated.
Actual captions??? I applaud you!!
Also excellent video!🎉
wikipedia: "The Atari 2600's CPU is the MOS Technology 6507, a version of the 6502, running at 1.19 MHz in the 2600."
In effect the same as the C64 but with an alternate set of peripheral chips.
Gotta love how your story sounds like a creepypasta at first.
i cant get enough of these. your voice is so nice to listen to, it helps me sleep! that and these are interesting as hell so I gotta end up listening to them over and over so they stop being interesting lmfao
That BPL instruction should have been BNE. And the checksum is calculated backwards. This is something that I very often do because DEY sets the Z flag in the status register. If you calculate the checksum forwards, you need a CPY instruction. Doing it backwards allows you to lose that compare instruction, but it does also mean that you have to store your text backwards too if using an offset to print text.
Nearly all additions require you to CLC before doing the ADd with Carry. The same as you SEC before doing subtractions. What you are getting wrong when you explain this checksum code is that the Accumulator is 8bits. It never reaches a point where you only look at the lower 8 bits because it's ONLY ever 8bits. Also if you look, the result of the addition is stored in Zero Page which some other code will need to check. That just involves an LDA and BEQ.
Looking at 5:40 in the video, using BPL did no harm except include the X-position into the checksum, just as the LDY #16 caused it to reach one value too far. It exits the loop when Y decrements into the "negatives" (255). This is a good way to include the zeroth item in a list sometimes.
You are right, he "shows" the addition happening forwards, when the processor is actually adding last term first. The CLC is only here so the carry flag starts from a known state - the carries that occur along the way have been expected and accounted for in the final check.
A thousand thank yous for this!
I just picked up a Tempest board and knew there was copy protection, but thought I was going to have to reverse this stuff for myself. THANK YOU! 👍
Tempest was my absolute favorite video game, bar none!!! On another note, my cousin was married to the late Jerry Logg, father of Ed Logg who created Asteroids :)
I ram into the Pac-Man check when I hacked the pacman ROMs on this channel, to get to the kill screen fast. I always hated the rom checks. But this one Ik tempest is actually sneakier because not gives the illusion it all works.
What if we just draw a black credit over the existing one? The Atari copyright will still be there, but there's just something over it preventing the player from seeing it.
This is a vector-based arcade game, so you're essentially drawing with light. Drawing with "black" is the same as drawing nothing. Though I suppose you could draw a solid rectangle over the text making it unreadable.
@@RGMechEx I see!! Thank you!
Super fun video! Anti-piracy is one of my favorite topics about retro games. Thanks for making this!
Anti-piracy caused me no end of heartbreak when I had my crappy R4. So much lost progress 😢
That's beautifully evil.
I love the old Atari vector machines. There's probably a video's worth of stuff to be done about the pseudo 3d math hardware in the atari mathbox. I have a bunch of documentation on it that I reverse-engineered, drop me a line if you're interested.
It’s tricky and clever, but I wouldn’t call it evil. These developers are trying to defend their software creations against pirates, after all. The legitimate creators and owners of the software are the good guys in this case.
A similar anti piracy method that was used on Spyro the Dragon on the PS1. If the game found it was a pirate copy, it would make later levels impossible to complete. But the hapless pirate would not find out there was a problem until he was a couple of levels in.
Dude I played Tempest on arcade back in the 80s 🤣 We had a bunch of arcade games at the daycare I went to as a kid. 👌
It's very intriguing to see the game basically corrupt itself in an effort to fight piracy. It seems fun!
No one knows how to break a game more than its own developers!
I would love to see more your videos about anti-piracy mechanisms. This topic is super interesting!
Man, they really only checked that one string, huh?
Honestly this just makes me wish I had a rotary dial or a real Tempest machine.
I love this game so much. So glad to know there's cool anti-piracy stuff in this game too!
I'm currently reverse engineering a H.E.R.O. C64 cartridge image. I'm finding that there are multiple locations where it technically writes break commands to code points in cartridge, but if the cartridge had been dumped to load from disk to RAM, these commands would corrupt the game and cause it to reset or crash.
I am amazed how much of Assembly Code I've learned from you, but it is astounding how little I understand even now
i find it extremely funny how atari decided that the copyright string _must be displayed at all costs_ and will prevent the game loading otherwise.
I know this would prevent most pirates from messing with the game and avoid lawsuits or smth, and yet i still find it funny.
I think the point was even if you cracked there was more ground to sue you into the ground for copyright infringement
THAT’S how Decimal Mode one the 6502 works‽ It’s so obvious in retrospect but I’ve been perplexed about it’s actual use for a while now- actually makes a lot of sense for the eta.
I read that Nintendo removed the decimal mode for their Family Computer/Entertainment System just to dodge the patent, so that's the one thing NES coders may not have any experience with!
Back then protection did work again piracy as there was no emulators and you need to buy hardware with the game or physical roms either way, they been againts bootleging and unlicenced use of hardware, for that all you needed was to force to use tradmarked logo or copyright to boot the hardware, so hardware force you to illegally (or else you got legal licence) use trademarks and they can chase you for that. Consoles used that too and used logos as a key to boot the game and display it on screen, most known example Game Boy or PlayStation 2