CGA on the Amiga. Wait... what?!
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- Опубліковано 29 тра 2024
- All Commodore Amigas can output digital RGB with intensity but did anyone ever use it? Let’s build an adapter and test it out!
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00:00 Introduction
00:15 Amiga Graphics
02:23 CGA and Digital RGBi
04:22 Building an Adapter
09:41 Initial Testing and Tweaks
12:40 RGBi Demonstration
20:00 Boot Problems Redux
20:54 ChatGPT
22:28 Conclusion
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Thank you for revealing that old mystery. I stumped on the digital video output when I was making a RGB cable for my A1200 back in the days and I was not able to find any information about what it was capable of.
You have Arkanoid skills.😅
I fully agree....
I'm really enjoying this "nobody asked for it" series and hope you can continue to find stuff to feature like this. As for CGA mode on the Amiga, yeah sorry but I'm going to stick to the good old native Amiga RGB modes (and RTG modes thanks to PiStorm). ;)
This feature was actually extremely useful in giving the Amiga a buffered high-bandwidth digital output. There was a whole class of display devices that took advantage of this feature -- DCTV (which constructed a composite signal using data sent over RGBI), and devices that combined two 4-bit pixels into one 8-bit pixel (HAM-E and Graffiti). Graffiti also introduced a semi-chunky mode using this technique.
While I don't know of any implementations that used this for anything other than graphics devices, you could conceivably have sacrificed lines of your display for any arbitrary sort of digital output.
I actually got to play with a DCTV for a while. It was interesting. Never played with a HAM-E or Graffiti.
That's super cool. I don't know anything about these devices. Another rabbit hole to go down I suppose :P
@@retrobitstv Yup -- OCS was perfectly capable of sending 8 bits of data for a 140ns ("lores") pixel, but it didn't have color registers for more than five bitplanes, and was only set up to be able to fetch six (for EHB and HAM). You could easily set it to 70ns ("hires") though to send 8 bits of data in the same 140ns, which could be interpreted by a relatively simple device. The device creators could ultimately decide how to interpret the data.
Since HAM-E basically implemented HAM8 before AGA, there was a rumor that Commodore actually asked Black Belt Systems to take it off the market.
Graffiti could do chunky pixels by buffering data that the software blindly wrote into the bitplanes. (The buffer is only 128 bits, so it's not a linear chunky framebuffer, but you could at least write 4 chunky 8-bit pixels at a time in a row in a single 32-bit operation, instead of having to convert to planar.).
HAM-Es are super rare and hard to get, and DCTVs are getting hard to find, but Graffiti is still pretty easy to get since it's a much more recent product and Individual Computers is still around.
@@NozomuYume C65 has 256 color registers with A500's memory bandwidth.
"It can also do...alot less" 🤣
I'm not sure if you normally crimp the way you did in the shot but it would explain why you are finding crimping challenging. In the video, you put the crimp in sideways, and in a larger section that doesn't match the crimp. The open part of the "U" on the crimp should be pointed downwards and as you press it together the "arms" of the U slide along the walls and bend back on themselves. The tool has two "steps" inside which line up with the two sets of arms on the crimp - one for the wire's insulation and one for the conductor.
Thanks for the pointers! I tried crimping it in the appropriately sized part of the tool but it never worked properly for me. Cheap tool perhaps, but willing to bet I was also doing something wrong. Found this method worked and ran with it, despite the low success rate. I will try again doing it the right way.
@@retrobitstv They are quite tricky even with a decent tool I think. I find that the crimps usually come a little more splayed out than they should be so I narrow them with some pliers first. Then I insert it into the tool, using the stepped part to position it then ratchet down until the crimp is held in place but not closed, which makes it easier to insert the wire the into the crimp. Judging how much insulation to strip back and how deep to insert the wire is not always easy though.
I was, with my human brain, thinking about Lemmings all along, given its colours were chosen to make porting to the PC easier. Awesome ball-juggling in Arkanoid, by the way.
Another great episode.
The first computer I had access to as a kids was an IBM PC XT clone with CGA graphics. I remember being annoyed by the 4 colors limit in graphics mode, while seeing all those glorious 16 colors in text mode. My annoyance only grew when I eventually realized that it was due to the 16K of video RAM, and if it had only 16K more all 16 simultaneous colors would've been possible. I mean, what's another 16K, right? Especially considering that the system had whopping 640K of main RAM! Anyway, I still had amazing fun with that computer, and many years (decades even!) discovered that there actually used to be a Tandy 1000 standard that did pretty much what I imagined as a kid. So, to this day it remains for me a kind of mysterious "what could've been"...
I liked this video, for a short while I had to use a RGBI on my Amiga due to an issue with my monitor ( Modified Magnavox Color Monitor 40). But was great meeting you at VCF east...
Great meeting you too! Cool, so there were definitely a few people who did use this capability back in the day.
I always wondered why commodore bothered with that gigantic 23 pin cable. Now I know something else was hiding in there
This would have been a perfectly serviceable option for people who only wanted to use Workbench-based apps in the 1.x era, which is probably all that the Amiga's designers were thinking about at the time. Imagine being a PC owner in 1985 wanting a more capable office machine with a GUI and faster graphics, and thinking a Mac might be a decent option if not for the tiny monochrome screen and large price tag. Then someone points out that for only $1000, you could have a machine with everything you're looking for plus you can keep your existing monitor. The people who gave it the ability to read DOS disks off an internal drive were definitely thinking about white-collar workers who wanted to take their work home with them. If only office productivity apps on the Amiga hadn't been a complete joke.
That worked better than I thought it would and I can totally see this as being the kind of "we shouldn't, but we will" project I would do!
Sometimes the curiosity experiments are the most fun even if they're impractical :)
I always wanted to try this!! Cheers for doing it. Now I don't need to bother lol.
I had a Commodore 64 back in the day, at first with a TV, then I got a monitor (an 1802 I think...or was it 1902? IDK), but at some point I ended up with a 1084S. Not sure if that was before or after I got an Amiga 500. Before, I think. So I never had to deal with connecting an Amiga to a monitor that took anything less than the 500's best, analog RGB connection and stereo sound. If I did get the Amiga before the 1084S, then I was at worst connecting composite and audio into a boom box. IDK, it's been like 33 years since I first got an Amiga and my memory isn't the greatest. A couple of friends of mine had to deal with using the A520 RF adaptor, connecting it to a TV set. That kind of sucked.
What I never saw at the time (1981-1984) was an IBM with a CGA card connected through a composite into a horrible TV and creating artifact colors. At that point I hadn't really been mixing with other nerds, at least not until I got on to the BBS'es (1989), so I didn't know anyone with a PC. My first modem, a 300bps Commodore user port cartridge, led to a 1200... then an A500 with a 2400, then I got a USRobotics 14.4K HST, which was Texas Instruments DSP based and thus flashable all the way up through 33.6K and finally 56K as the standards evolved... serving into my PC years... expensive yes but worth it, definitely... used it for like a decade... then eventually on PC I got a cable modem. Now I'm using my phone to feed a hotspot to my PC. How droll. And I'm rambling. High, world.
Anyway, I understand that it's mostly Sierra that took advantage of that CGA composite artifact color hack. Most developers stuck to the RGBi CGA 4-color (ugly) palettes and until VGA came out (EGA was a step up but still not great, compared to Amiga) PC graphics weren't considered "pretty."
I didn't get into PCs until the VGA era so I never really messed around with CGA or EGA very much. I didn't find out about CGA artifact color until much later. If you haven't seen Area 5150 demo from 2022, check that out for some mind blowing CGA colors!
In the late 80's I build a cable to do just this with my 1902 monitor. I hated every second of using the Amiga like that. I ended up going into debt (more so) and buying a multisync.
This is probably the topic i never thought anyone would cover, i enjoyed this very very much, incredible video as always... since i always wanted a digital rgb monitor for my old c128 back in the day, and later got the amiga, now i see that i was probably for the better that i didnt get one ... anyways, keep up with good subject, perhaps i can suggest one topic i always wanted to see, that is hooking up 5 1/4 inch floppy to amiga, and use diskchange DF1: to let amiga know that disks are changed, yes, 5.25 floppies dont click :) so i guess when one makes this kind of video i will be happy to see it in action :)
I bought a monitor from Goodwill a year ago that was only sold through a Sears catalog. It has a RGB in socket in the back. I got excited and went down the rabbit hole to find out it was actually the digital rgb showing in this video and not the kind you mod your game consoles for. Finding the proprietary cable for it was also very hard to do. I still have no use for it and was saving it for some obscure computer that might take advantage of it.
Did it look like this? iec.net/product/pc-cga-to-sanyo-or-amdek-3-monitor-cable-6/
Not too long ago I reviewed the "Sears Total Video System" monitor (really a rebranded Sanyo?) that was also sold as "LXI" that used this type of RGBi cable.
@retrobits yep that's the cable. The TV has a side panel with adjustable knobs. You likely did a video on it. Cool screen but I haven't found any tech that warrants it.
@@kenmys Yea as a computer monitor it's kind of limited by its consumer-grade TV tube. Still works fine in a pinch for a C128 or Tandy 1000 though :)
CGA = Completely Grotesque Aesthetic
Hopefully some demo group makes a demo specifically to push CGAmiga graphics :) Since everything else is a compromise. Sit an IBM 5153 on my Amiga 4000... oh the inhumanity of it... poor Amiga.
I absolutely love these fringe or unusual cases with retro-hardware. Sure you wouldn't use it, but it still shows the versatility of the Amiga. ChatGPT is awesome but watch out for it's hallucinations. I was messing around getting it to generate 6502 code but it kept "forgetting" the registers weren't 16bit
Funny you mention that! I asked ChatGPT to generate a VIC-20 basic program to draw a circle on the screen and it first tried to use a graphic mode, which the system doesn't even have. It failed 2 or 3 more times do do anything useful before I gave up on it. Maybe v4 is better but I don't have access to that :P
@@retrobitstv In some ways it's comforting that us humans still have some value - for the time being anyway ;-)
interesting and entertaining beats practicality
Wow you can play Arkanoid so well 😎kudos.. great video.
Hehe! Look at that, one learns something new every day... Thank you very much! 👍
I actually have the RGBi cable and it works on my Magnavox monitor. Same monitor as the Commodore 1084s just Magnavox branded. Super clear for workbench and applications, not so good for art programs or games though.
Cool! Do you remember where you got the cable from?
@@retrobitstv I think that I bought it off of ebay like 17 years ago. LOL!
It is way easier if you first crimp the connector on the wire, and only then break it out of the "rail".
I never even thought to try that. I will give it a go next time. Thanks for the tip!
The aga machines can show 262000 colors not 4096
I have a VGA adaptor I've tested but it limits me to one monitor and precludes connecting to a capture card so I prefer RGBi to SCART then SCART to HDMI (lots of try it and see in the past)... so I've tried similar.
I think the issues was that you had 2 grounds connected cga monitors were likely not designed for using multiple terminals at once either/or principle of operation
No wonder you hate the crimp terminals when you are using the wrong crimp tool, lol.
I never claimed to know what I was doing :) I bought that tool because it claimed to be able to handle that type of terminal but I'm probably using it wrong or maybe it just sucks.
@@retrobitstv If everyone knew what they were doing, there would be no need to learn anything or have vocations, so you are in good company, no need to feel bad for not knowing something 😉
cool
Commodore 1084S, the rectangular from Philips, had TTL input.
Also a cable was included, but it was for the C128 if I remember correct.
EDIT: aaaand you said it later in the video 😀
Did you spot any latency with the digital input?
I don't believe there to be any latency as it's not a digital bitstream that needs to be decoded or processed.
@@retrobitstv Thanks
AFAIR, CGA has only 2 palettes of 4 colors in 320x200 graphics mode, not 3 palettes. Am I wrong?
There were two 'default' palettes (0 and 1) - the third palette (cyan, red, white, black) was obtained by doing register tweaking.
There's a third "undocumented" palette as well. From wikipedia: "Mode 5 disables the color burst to allow colors to appear in grayscale on composite monitor. However, unlike the text modes, this also affects the colors displayed on an RGBI monitor, altering them to the cyan/red/white palette seen above. This palette is not documented by IBM, but was used in some software."
PC I PC II and PCIII were CGA? Using C= monitor?
I've never actually seen one of the Commodore PCs but assuming they all used CGA then they would have worked with any existing C128 monitor.
Brown is just dark yellow. Technology Connections channel did a great, albeit long video on it. Why you never see Brown lights.
I have a 23 to six pin round cable looks like that is a CGA cable I have! I bought 3 monitors 3 yrs ago lol
The Philips 1084 monitor has two round DIN connectors. If it's a 6-pin connector it's for the analog RGB and if it's an 8-pin connector it's for the digital RGBi.
@@retrobitstv I have a Teknika MJ22 And its RGB with 8 pin round IB PC and Jr and apple III IIe Per booklet
who knows if making a driver for the workbench would get something more from this video output (like a "DigitalNTSC" in ScreenMode Preferences), but probably it would be useless
4:54 Did you cut that?
I bought it from a vendor that made them, I didn't cut it myself. This was years ago.
@@retrobitstv That's good.
For the next "nobody asked for it" what about a Sega Megadrive hackintosh, with system 7
I disagree about your statement that CGA was the de facto standard until EGA superceded it. Due to the much higher cost of EGA, CGA stayed the de facto standard until VGA became cheap enough to replace it.
What about PGC, or Professional Graphics Controller?
@@MicahtheDrumCorpsPseudoboomer Basically nobody had one - it was half the price of a PC XT, so it was only used for CAD
Not new news as I bought my 1084s for my C128 and used it for my Amiga. Then I ran my first PC with CGA
My 1048S is still here next to me working strong
The 1084s is my favorite monitor because it's so versatile. That said, if you had one from the c128 (as I also did), it would have supported the Amiga's analog RGB out-of-the-box so there would have been no need to use the inferior digital RGBi.
Even chá in Amiga is better then original, compare that with Monkey Island PC cga
dark yellow is brown.
Crimp connection = best connection. You just need the proper tools.
Playing dune 2 on a monitor is much better
what a crime, i was shocked and disgusted when i learnt about CGA, EGA and actually even VGA garbage PC users had to endure vs what the amiga had.
Hah... junky. Thanks buddy.
Haha... HAM images in CGA 😂 Love it.
Hey you're pretty good at Araknoid... or was that the demo mode... 😏
I bet Lemmings would have looked semi-OK. How about Shadow of the Beast!