Have you tried changing the floppy drive ribbon cable? Or the floppy drive?

Have you run an mtest86 stress test?

Also, have you tried setting L2 cache to WT instead of WB if that is set as such? Finally, how much cache does the MB have and are jumpers set correctly for that, is it reported correctly at POST?

Gmlb256 wrote on 2022-06-21, 20:51:

Datadrainer wrote on 2022-06-21, 20:26:

Anyway, I would stay on MS-DOS 5.0/6.x for a 486 DOS PC. Why would you use MS-DOS 7.x? For the long file name support?

The only practical reason is FAT32 partition support for MS-DOS 7.1 unless the OP wants to run Windows 3.x (and certain low level disk utilities) without any compromises and/or doesn't need more than 8GB (each FAT16 partition is limited to 2GB).

Windows 3.0 or 3.1 might be not affected, maybe, since they don't use VFAT.
Windows for Workgroups 3.11 uses it first time.

If Windows support isn't a high priority, Windows 3.0 MME might be good enough.
It's essentially Windows 3.0 with sound card support.
The Tandy version ships with an SB16 driver, I think.
Just don't forget to get a copy of WINA20.386 (place it into C:\ or SYSTEM directory).
Microsoft didn't ship it with Windows 3.0.
Instead, it shipped it with MS-DOS 5.0! Sneaky, huh?! 😏

Gmlb256 wrote on 2022-06-21, 20:51:

Datadrainer wrote on 2022-06-21, 20:26:

Maybe FreeDOS would be a better option as it have a lot of useful programs compatible with LFN included.
Edit: And the like for FAT32 support.

FreeDOS isn't still 100% compatible despite improvements in recent versions and most (if not all) of the utilities can be used with MS-DOS without any problems.

That's right, there's an experimental FreeDOS kernal, but.. Ugh. 😒
Anyway, Windows 3.0/MME or 3.1 in Standard-Mode could work.
That might be good enough for most scenarios.

Sound, SVGA and things like Video for Windows 1.0, Autodesk Animation Player or 16-Bit QuickTime could work already.

Especially, since no virtual memory is needed if the PC has enough physical memory.
It will be even quicker in Standard-Mode, which kind of is a contradiction.

Things like Win32s or WinG won't work, of course.