Most compatibility issues in DOS 7.x are because DOS 7.x has standard values for all that stuff you normally set in config.sys and autoexec.bat in previous DOS versions - it actually has these embedded into IO.SYS. E.g. STACKS, FILES, BUFFERS, etc. If you don't set them in DOS 7.x, they have different values compared to a standard - say - DOS 6.22 installation. STACKS and FILES especially can heavily affect compatibility with very old DOS games, so you need to make sure to have them set correctly in DOS 7.x and not using the default values.

And strictly speaking, there is no MS-DOS 7.0 or 7.1. It's the DOS mode of Windows 95, not MS-DOS 7. Just like Windows 7 is not Windows NT 6.1.

There IS difference between DOS 7.0 and 7.1 Windows 95 is built on top of 7.0 and Windows 98 is on top of 7.1
I've set STACKS=8,128 like BioMenace Help file says, but it didn't help.
I've played this game back in 2000 on a Windows 98SE machine and never had problems. But I can reproduce this bug consistently with Windows 95 installation.

Windows 9X is not built on top of DOS. It uses it as a bootloader and compat' layer, and sucks its brains out and takes total control of the machine once booted.

Lady Eklipse wrote on 2020-03-01, 10:35:

There IS difference between DOS 7.0 and 7.1 Windows 95 is built on top of 7.0 and Windows 98 is on top of 7.1
I've set STACKS=8,128 like BioMenace Help file says, but it didn't help.
I've played this game back in 2000 on a Windows 98SE machine and never had problems. But I can reproduce this bug consistently with Windows 95 installation.

It is a known bug in Bio Menace. Don't remember the details, but something is not properly initialized / corrupted, which causes it to read random garbage. It may be that by accident, the values of the random garbage are different for different DOS versions.

Edit: The bug and fixed are discussed in this thread. Apparently STACKS=9,256 is needed to 'hide' the bug without the patch.

Just wanted to point out that only the original Windows 95 retail version and Windows 95 A (aka OSR 1) came with DOS 7.0. Later versions of Windows 95 (OSR2.x) came with DOS 7.1 which also introduced FAT32 support.

dr_st wrote on 2020-03-01, 11:36:

Lady Eklipse wrote on 2020-03-01, 10:35:

There IS difference between DOS 7.0 and 7.1 Windows 95 is built on top of 7.0 and Windows 98 is on top of 7.1
I've set STACKS=8,128 like BioMenace Help file says, but it didn't help.
I've played this game back in 2000 on a Windows 98SE machine and never had problems. But I can reproduce this bug consistently with Windows 95 installation.

It is a known bug in Bio Menace. Don't remember the details, but something is not properly initialized / corrupted, which causes it to read random garbage. It may be that by accident, the values of the random garbage are different for different DOS versions.

Edit: The bug and fixed are discussed in this thread. Apparently STACKS=9,256 is needed to 'hide' the bug without the patch.

So, you're saying it might be that only my installation of Windows 95 is for some reason prone to this garbage and I was able to run the game without problems in DOS 6.22 and Windows 98SE out of luck? I ran the game back in 2000 and had no this bug, only Windows 95 causes problems, hence my conclusions. 😀

Lady Eklipse wrote on 2020-03-01, 12:31:

So, you're saying it might be that only my installation of Windows 95 is for some reason prone to this garbage and I was able to run the game without problems in DOS 6.22 and Windows 98SE out of luck? I ran the game back in 2000 and had no this bug, only Windows 95 causes problems, hence my conclusions.

All I'm saying is that what you see as some "incompatibility issue" of a specific DOS version, really is just a bug in a particular game that just happens to manifest itself differently (maybe randomly) on different DOS versions.

Or do you have any game other than Bio Menace that doesn't work?

I can tell you for sure that I've experienced the same bug on my Win98SE pure DOS mode and even in DOSBOX, until I patched Bio Menace.

xcomcmdr wrote on 2020-03-01, 11:31:

Windows 9X is not built on top of DOS. It uses it as a bootloader and compat' layer, and sucks its brains out and takes total control of the machine once booted.

Well, it still uses some DOS functions, even in 32-bit mode, as you can see from the last paragraph of Raymond's post:

Now, there are parts of MS-DOS that are unrelated to file I/O. For example, there are functions for allocating memory, parsing a string containing potential wildcards into FCB format, that sort of thing. Those functions were still handled by MS-DOS since they were just “helper library” type functions and there was no benefit to reimplementing them in 32-bit code aside from just being able to say that you did it. The old 16-bit code worked just fine, and if you let it do the work, you preserved compatibility with programs that patched MS-DOS in order to alter the behavior of those functions.

derSammler wrote on 2020-03-01, 10:23:

And strictly speaking, there is no MS-DOS 7.0 or 7.1. It's the DOS mode of Windows 95, not MS-DOS 7. Just like Windows 7 is not Windows NT 6.1.

Eh, I'm not sure that "strictly speaking" this is true at all. For one thing, Microsoft was working on the next version of MS-DOS after 6.x, per an interview with a Microsoft employee as seen on some episode of The Computer Chronicles I saw one time (I'm really good at references </sarcasm>), and that ended up getting rolled into Win95. So it was conceived as a product in its own right, it just never got released independently. Despite that, Win95's "DOS mode" is fully functional as its own standalone operating system, reports itself as DOS 7.0 (or 7.1, depending on the release), and comes with a reasonably full suite of DOS commands in C:\Windows\Command.

So... what exactly makes this not a true DOS? That it never shipped in a retail box? That it doesn't create a C:\DOS directory? That's all splitting hairs. Certainly doesn't matter when it comes to deciding whether to use it sans Windows.

The only compatibility issue I've ran into myself is trying to run Creative's PNP Configuration Manager (CTCM). The installer refuses to run when %winbootdir% is set. Unfortunately, Microsoft saw it necessary to set this even in DOS mode, so the installer always thinks it's running in a DOS window. The CTCM/CTCU executables also check for this, but it's easy enough to search for the string with a hex editor and change it to something else (I chose winbootder) so that the match always fails. The installer, I think, is compressed so I wasn't able to find the string in the file. I just used a DOS 6 box to run the installer, then copied the files over to the DOS 7 box. (Would've been easier if I hadn't manually created an LBA partition, which a DOS 6 boot floppy couldn't read.)

I found a pre modded release of CTCM where someone had changed it to windootdir, thought it was funny so I've been doing it that way since.

Were any two different versions of dos guaranteed to have 100% compatibility?

BinaryDemon wrote on 2020-03-03, 02:43:

Were any two different versions of dos guaranteed to have 100% compatibility?

It depends. MS-DOS 6.x was very compatible to MS-DOS 5 on the kernal level.
MS-DOS 5 in turn was compatible to MS-/PC-DOS 3.30.. So maybe a newer IBM PC-DOS is worth a try ?
- I'm not sure. Mainly used PC-DOS 3.30 for maximum compatibility with 1980 software (Windows 2.x, Clipper, dBase etc). 😐

If 90% compatibility is good enough, Paragon DOS/PTS-DOS is worth a try, too.
At least one of these Russian DOSes is said to comply to military standards, so it can't be junk.

FreeDOS.. Well, it's still in development. But in improves. Slowly. step-by-step.
The experimental kernal which can run Windows 3.1 is worth a try, too, I suppose.

Edit: There are also DR-DOS, Novell DOS and Caldera DOS, of course.
Though, becaue due to lack of testing I'm unsure how compatible they are.
I wished I could recommend them, as much as I'd like PC-MOS/386 v5.

Edit: I did forget something. I had a 286 for a long time when I was little.
Unfortunately, a pure 16 bitter can't run MS-DOS 7.x, so I never did much testing on DOS 7 when I was still into PC games.
On my father's 386DX-40 I mainly played some of the early Win32s games, like Hyperoid. Or demanding DOS games, like a MIG29 flightsim.
Okay, I also played some of my beloved Win16 games on his PC. Because he had a gigantic 20" monitor (mine was lousy ~12-14"). 😁

Lady Eklipse wrote on 2020-03-01, 09:44:

Hello,
I'd like to share my experience with Windows 95 OSR 2.5 DOS and compatibility issues.

90% of all issues I had with Windows 95/98 PCs running DOS were caused by ...
a) speed issues
b) having too much memory or other memory issues
c) having 2D cards that weren't very DOS compatible
d) Sound card incompatibilities

I did have the odd game that wouldn't run for some reason which might be due to software incompatibility but most was caused by the actual hardware.

red_avatar wrote on 2020-03-07, 20:16:

90% of all issues I had with Windows 95/98 PCs running DOS were caused by ...
[..]
b) having too much memory or other memory issues

That is one thing that has definitely changed this go-around. I had to patch Duke 3D to install with 64MB RAM. Back in the day, I was happy when I had enough RAM for it to run at all. 🤣

SirNickity wrote on 2020-03-09, 20:22:

I had to patch Duke 3D to install with 64MB RAM.

There's an easier way to solve "too much RAM" issues - make a ramdrive and have it eat all the excess memory.

I use XMSDSK.EXE for this purpose and it allows me to run games that normally won't even start if you have more than 32 MB of RAM, such as Aladdin.

Joseph_Joestar wrote on 2020-03-09, 20:30:

SirNickity wrote on 2020-03-09, 20:22:

I had to patch Duke 3D to install with 64MB RAM.

There's an easier way to solve "too much RAM" issues - make a ramdrive and have it eat all the excess memory.

I use XMSDSK.EXE for this purpose and it allows me to run games that normally won't even start if you have more than 32 MB of RAM, such as Aladdin.

Yeah I have XMSDSK installed just in case - I got 24MB of RAM and if a game won't run, I try to decrease it to 4MB just in case. So far it didn't fix any games but it's nice to have the option. I hear 32MB and 64MB are the real limits that cause problems.

I don't run into that problem too often. I desire to own more retro PCs than I have any need to own, in all honesty, so I tend to spread out software to exactly the era of hardware it was meant to run on, since at least then it has a purpose (aside from being the target of my adoration.)

Duke 3D was kind of an outlier, since it runs best on a Pentium vs. my DX2/66 for e.g. The Pentium has 64MB, the DX/2 has 16MB. I could remove half and maybe one or two DOS games would be happier, but it's a Win95 box that I boot into DOS mode, and '95 loves itself some memory. 😀 And, 3D Realms issued a patch that fixes it, so... meh.

maxtherabbit wrote on 2020-03-03, 01:53:

I found a pre modded release of CTCM where someone had changed it to windootdir, thought it was funny so I've been doing it that way since.

I'm glad that my joke carries on. 😀

Thanks for this thread! I have a fresh WFWG (FAT) with 6.22 (updated DOS with 7.0 updates) and 64MB RAM.

I have had an issue running Perfect General 2 where it reboots the machine when trying to start. Never had that problem before. After reading this thread, I will reduce the RAM to 32MB when I get home from work tonight and see if that solves the problem.

..... And, it worked!

You folks are awesome!