Are x86 programming questions on-topic?

Question

Do questions like these belong on Retrocomputing?

• How to write directly to video memory in MS-DOS?
• Why the "jmp" instruction is not working?

It looks to me like questions like this should be on Stack Overflow. They are about how to program on a specific assembler language. Just because it happens to be an old language...

I think it's one thing to ask about how the CPU architecture works, in which case they would clearly fit. But these questions are about the syntax of intel ASM86 and a general misunderstanding about how machine code works.

Or maybe it's just because I'm used to seeing such questions in Stack Overflow. Obviously, the community decides.

Answer 1

The two questions that you mention could be taken differently.

The mechanism of writing to video memory was not always obvious on retrocomputers. The format of data could also be less than clear. So in this case, a question regarding technique is suitable here.

Why is my JMP not working is more problematic. The bug in that question could be introduced in a similar way in a modern processor. Although I suspect most modern assemblers would pick up the difference between code and data. If the wording of the question specifically related to understanding some feature of old assemblers that is different to modern practice then it would be on topic. However, I don't believe we should be a debugging service.

We have questions on the site regarding the instruction sets of older generation processors. These don't ask for fixing a specific program but for understanding of the operation of certain instructions. Perfectly good for the site and its future readers.

"Write my code for me" is off-topic on most StackExchange sites, including StackOverflow. If that is the limit of the extent of a question, I suggest that it should also be off-topic here.

Answer 2

I would agree with the statement "This site should not be a venue for fielding x86 programming questions". However, the two examples of actual questions seem much more about "retro-programming" on "retro-computers" than x86 programming.

The one about the jmp instruction is asked in the context of using a legacy assembler included with MS-DOS. The problem turned out to be a trivial programming error, but someone attempting similar things on unfamiliar retro platforms could have just as easily encountered a problem more related to the old technology that they were interacting with - making it relevant for this site.

The question about accessing video memory was kind of naive, in that the OP seemed to think something more complex than a hard-coded address reserved in the memory map was at issue. I think a really descriptive answer for that could have expanded on the simplicity of early PC's, and their lack of any sophisticated protocol for assigning hardware resources, like memory space, to peripherals during system boot.

To some extent, at least, it is up to those posting answers to expand on the topic enough that the answer is both complete and also educational from the angle of understanding the retro-tech. That care and attention will make for better answers and a more useful site, I think.

Answer 3

In my opinion - First one is on topic, because it asks about something in a retro operating system, that can't be, or at least can't be easily replicated in another OS. None other site is more on topic about MS-DOS than ours, so it's on-topic.

The second question though.. It asks about a problem that can be replicated on a modern OS without emulation. Even if it shows that it doesn't work in retro operating system(DOS), it still won't work in any other OS as well. This question can be as well moved to another page like Stack Overflow, and it may benefit from the move.

Answer 4

Personally I still have a hard time to think of PCs as retro, but they are. Just because something targets x86 doesn't turn it off topic. It's all about the usage framework the question belongs to. Asking a question in a community like Retrocomputing already shows that the poster isn't exactly asking for the latest protocol to transfer a stereo image over PCI to some 3D goggles.

Without further information I would always assume that such questions are meant to reside in a basic, 16 bit x86 environment. Even thru there are many similarities between an 8086 and a x86-64 capable Opteron, they are quite distinctive environments with different answers.

Just imagine a question about the best way to multiply an integer value by 5. For modern x86 the answer is clear: LEA will do the trick with a scaling factor of 4 and twice the source register. Just, prior to the 80386, LEA didn't have the scaling ability. So I'd answer the same question in Retrocomputing with a combination of move, shift and add.

So, as hard as it feels, x86 is on topic for Retrocomputing and different from Stack Overflow.

Answer 5

Do you mean Intel x86 processors from the 8-bit to 64 bit versions? Or do you mean PCs based on these running Microsoft DOS and Windows, which is a much broader topic?

For just the processors, I'd say anything that went obsolete long enough ago to now have some nostalgic interest is on topic.

So 8080, 8086, 8088, and 286 are definitely on-topic. 386 is probably on-topic considering that even the Linux kernel just dropped support for it. There's surely a range of old stuff that worked on 386 systems that doesn't work on modern systems. These days I think a decent argument can be made through 486 and Pentium. Maybe not for all 32-bit stuff though since I think 32-bit stuff is still being made. One of my netbooks is 32-bit but doesn't seem at all retro. Anything 64-bit can't be retro yet, even though it's been around for years now.

Stuff like Real Mode and Protected Mode and segmented memory models and DOS extenders are surely on topic.

Any OSes that don't run on current systems are probably on-topic. Real DOS is probably always on-topic. That doesn't mean all Windows console stuff is on-topic. People probably still confuse the two. OS/2 is probably on topic, unless it's still made?

Stuff about old versions of Windows prior to Windows 2000 is surely on topic since that's when all Windows versions were based on Windows NT and the versions based on DOS became obsolete.

Look, "retro" in general means that it went old and boring and after some years became interesting again to a certain community, generally out of nostalgia. So if it's clearly still just "old and boring" it has no place here. If it did its time in the "old and boring" phase and then regained interest, then it's on-topic. There will be a blurry line between that might warrant discussion sometimes.