I'm not going to use any windows on my 386, therefore 4dos should be okay and stable?
Do you have any alternative for DOSMAX?

4dos was okay with what I and my colleagues did back then (mainly editor, compiler, debugger).
But it conflicts with some internal DOS things and for this I would not have it loaded when doing stability tests - you else cannot be sure about a problems' origin.

DOSMAX - what do you want it for? aren't the 600+k sufficient that can be used with stable and reliable methods?

I'll check, if i have problems with original command.com.

Dosmax - because i want to try to get the absolute maximum out of the 640k. I'm at about 628k.

On some 286, 386 and 486 chipsets, you can actually go even further ! 😁

It's called UMBDRVR and it lets you use some UMB without loading HIMEM.SYS/EMM386.EXE ... and you can even load HIMEM.SYS high !!

Deksor, like RDOSUMB, i'm already using. 😀
Also, JEMMex does quite a nice job.

Okay, played around a little.
I moved away from 4DOS to classic command.com, removed the DOSMAX, yet problems persisted - machine starts to behave a bit weird (as described above) and soon locks up.

Any other ideas, i could try out?

I was just scanning around the threads about this motherboard and found this out.

I found the culprit, and it was not about the motherboard. My big Sound Blaster 16 (CT2830) was the cause of instability.
While not sure, why it caused those problems, replacing it with another Sound Blaster 16 (CT2940) fixed all issues with that computer.

So a bit of necro for the thread, but at least this thread is closed. Hopefully helps someone in the future.