Відео

You made all that sound quite straight forward and approachable which is saying something when you're introducing assembly!

I want to write an OS that sits atop MS-DOS that runs on ELF, similar to how Windows 3 uses NE. Lol.

Your content is super accurate. But are you using voice changers or robotic voice - it is so boring to listen to it - so many times turned off the video.

You keep talking in past tense but they are megabytes if you are speaking in past tense.

You completely forgot to mention unofficial "unreal" mode, where you first switch the CPU to protected mode, extend the segments to 4GB and switch back to real mode. Boom, you can now access full 4GB of RAM from real mode, with real mode DOS, drivers, TSRs, etc. all functioning normally.

When I worked on my first PC, knowing it could have 640k of RAM, it seemed, and it was, an inexhaustible ocean of RAM.

"You are more ugly!"

QEMM

That was great, thank you!

I remember back in the day having a 20MB 386 that was tricked out, and having to have a multiple choice config / autoexec depending on what I needed as I didn't have enough base / umb / himem to get all of the drivers in and be able to run a half decent dos game. one config also had a 16MB ram drive that copied games I would play into it and run the game from ram. it was a long copy time, but games ran fast.

If i remember correctly one can generate COM files with the DOS debugger, too. No need for an assembler 😊

Dr. DOS was VAASTLY superior to CRAP DOS, and EVIL M$ tactics destrpyed it! .....NO FORGIVENESS!!!!!!!! EVIL EVIL EVIL EVIL!!!!!!!!!!!!!!!!!!!!!!!!!

The worm reverse code appears to be: Compare obj-velocity-x with “direction to Jason” (stored in $01) the EOR is a quick way to see if the signs match or not. BPL decides no reverse (bit 7 matches - ie the worm is going towards Jason) Then the reverse code is: Set velocity to F (going right) If vector to Jason (LDX $01) is left, then negate. Store result in obj-velocity-x.

Do you have the commented disassembly posted on GitHub or anything like that? I’d be happy to contribute my own findings. I’m interested in poking through the audio engine and music pattern data.

This is pretty cool! I just got into 8086 - 80486 era and memory management of the 1MB barrier in real mode and protected mode. If only I was more into it when I was younger lol

Best game ever so nostalgic

8:45 "Extended Memory - XMS maps extended RAM to UMBs". What UMBs does XMS use? or does it use conventional memory?

Mebibyte... Ugh.

1:58 you forgot the 186 2:33 the 286 was only mostly compatible, it didn't roll over at the 1MB limit like the 8086/8088 and 186, which is why the A20 gate was needed 3:00 the 386 can run real-mode apps in protected mode using virtual 8086 mode

Is the code published somewhere?

this is a great video, subscribed

This is awesome, I look forward to seeing much more.

The difference between the 8086 and 8088 is that the 8086 has 16 of it's address pins duplexing as data pins, while the 8088 only has 8 of them duplexing as data pins, but they are otherwise identical. This means that the 8086 is capable of accessing it's memory 16-bits at a time instead of 8-bits like the 8088. What I'm curious about is whether or not any motherboards actually implemented this. Given that the 8086 was more popular among business-oriented machines, I'm guessing somebody did, but I'm not familiar with any specifically.

Do you have a GitHub page?

Nobody who used a computer in that time would call a megabyte "mibibyte".

From my experience the memory area above 640 Kb was only available as RAM when a memory manager program like 386MAX or QEMM was installed. DOS 5.0 and higher has a similar memory manager included. Plus you could only do this on a 386 or higher CPU. There were some DOS games that needed this because they needed 600 Kb+ of RAM to run. These memory manager programs also supported the EMS memory interface in software by reserving a 64 Kb UMB area. They also scanned the entire upper memory area to map all free UMB's which included unused areas that were reserved for the system BIOS Typically these programs would load device drivers and TSRs into these recovered UMBs.

the good old days of messing with autoexec.bat and config.sys to to free up memory to maybe run a game

You just have to know your config.sys and autoexec.bat files.

"We'll never need more than 640K " - some guy that was completely wrong.

ms tres

To get Falcon3.0 with expansion packs running.. you needed to know all this shiet in this video - front and back.

The first KB was not occupied by the BIOS. It was RAM and was the BIOS Data Area (BDA); the values were populated by the BIOS. The first KB was actually the Interrupt Vector Table (IVT), then came BDA values for items such as COM/LPT port addresses, memory size, keyboard buffer, soft reset behavior, etc. MS-DOS boot sector would load initial code to 0:7C0, and would use 70:0 as the DOD data area.

Bah humbug, I think no one needs more than 64k 😂

The music goes hard

no, el 8088 es una variante del 8086, mas economica, el 8086 es de 1976 y el 8088 es de 1979

Talk about a blast from the past! When I was a teenager (pre-internet), I remember fighting with DOS and reading deep into manuals to squeeze out every free byte of RAM for my games. It could be quite intricate, and it took a while. It was almost like a game itself to find the right combinations.

i got specialty smartdrv, mouse, mscdex, and this special emm386(don't think it was qmm) that could use hard drive space as "ram" is you didn't have enough for a game, I used it to try to run magic carpet, on my 4mb 486 sx 25, packard bell. My computer did com with all these util Free cds. I did manage to get 621 free after all that. Does anyone know where I might find a Dos app called no.exe its usage would be zipping all contents of a folder with pkzip, so after zipping *.* no *.zip del *.* So basically one could make a batch file, to add hidden attribute to the prompt but i liked the exe because it was shareware and because it told you to pay or else. leaving you with just your zip. I would use it to compress on the fly different games when i wanted to play them and only a 250mb hard drive. I can't find any info about no.exe I also made a dos 62 and arachne and a ramdisk to book off single floppy with dos network support and mouse etc. I was always trying to push a limit somewhere.

We have the well known example of the "Hello World!" program. This was first run over 40 years ago on real IBM PC hardware and also run on many PC compatible computers. This was practically the simplest program that could be written for MS-DOS. Now unless we have a historic restored IBM PC or PC compatible computer we have to run it on a DOS emulator.

What a nice stroll down memory lane, pun intended.

Just found your channel and I'm really enjoying these!

I* was interested to watch this movie. But when I herad the computer voice, i stop watchin after 11 sec

"What about one eighty-s-" "Shhh, we don't talk about 80186."

this is neat. this was the explainer i needed 20 years ago. this is a summary of my decades of confusion and learning and 'eventually sorta getting it'. its great to see this all summarized in this way. it really is the top of the pyramid for an explanation of all of this history.

I remember once in 1990's I made a (test) program for bank switching with himem.sys :) At that time my data usually fitted in the 640K RAM so I did not used bank switching for anything more than test.

What memory management? Who in their right mind cares about DOS 6.22 in the year 2023?

Popped up recently for me too. I don't think HIIMEM or 286 can do UMB mapping though, that needs EMM386/QEMM and the v86 capability of the 386. I might be misremembering, but I think expended memory or LIM EMS (Lotus Intel Microsoft) was originally intended to allow bigger 123 spreadsheets RAM on an ISA card was mapped into (original spec, a 64k page frame of 4x 16k pages) similar to the way 8 bit home computers mapped extra ROM and RAM.

EMM386.EXE *twitch* HIMEM.SYS *flinch* oh no my ptsd

I remember using this - it was a nightmare!

First time I've ever heard someone unironically say "mebibyte", but good high-level explanation of a low-level topic. High level because questions segment/offset and selector/offset weren't discussed, nor why some things require you NOT run EMM386 but might work if you had an EMS card installed, how DOS could see memory above 1MB in real mode, why load order mattered as much as memory locations for where drivers went in memory when running memmaker, etc? That sort of thing … For how "simple" it is, MS-DOS memory management was a BIG topic. Might be too low-level for your audience though.

What does the address space look like if you did not have 1MB of Memory , specificaly if you only had 156k of memory; where does the BIOS, expansion ROM and Video?