Maybe the software is corrupted.

Not the case... On the last motherboard that I tried (Acorp 5TX29), I used the same disk that I use for benchmarking many other platforms. I had just played the game one week ago on an Asus P5A (Super Socket 7) + on tens of other boards in the past.
It really does seem that the issue is directly related to the 430TX chipset. Even though I tested this game on this chipset in the past, it seems like I never played it for more than a few minutes (and assumed that all was fine).
If anybody else can try it on their 430TX platform, I would be grateful 😀

Ok so you are trying to play a 1991 DOS game designed for a 386 on a TX motherboard with Pentium MMX.
What CPU did the Asus P5A have on it ?
Many things can make that game not run proper, not just the chipset.

I tried playing a 1991 DOS game on a platform that is known for its flexibility and is actually recommended for DOS gaming. The Pentium MMX can be slowed down to various 386 & 486 speed levels with great ease, which is why people choose it for DOS / Win 95 gaming

However, the main problem is that Prehistorik is not really a speed sensitive game (its speed sensitivity is usually just related to sound).
I, for one, have successfully played this game (and was able to reach the second, third and fourth levels) on platforms such as:
- Socket 3 (ASUS VL/I-486SVGOX4 with an Intel 486 DX4-100 CPU)
- Super Socket 7 (both Ali Aladdin V and VIA MVP3 chipsets) with various AMD K6-2+ CPUs.
- Slot 1 (Intel 440BX) with Pentium 2 Deschutes / Pentium 3 Coppermine up to 1 GHz
- Slot A (AMD-751) with AMD Athlon "Pluto" @ 750 MHz
- Socket 370 (Intel i815) with Intel Pentium 3 Coppermine/Tualatin
- Socket A (VIA KT400 / KT600) with AMD Athlon XP Thoroughbred and Barton CPUs (and this is usually my go-to Windows 98 / DOS platform)
- Socket 754/939 (VIA K8T800) with AMD Athlon 64 3800 / 4000+
- Socket 478 (Intel 865) with Pentium 4 Northwood 3 / 3.2 GHz

So... the fact that I get this problem only with 430TX/Pentium MMX is pretty weird (and, again, this happens with three different boards/CPUs and multiple VGA/sound card combos).
The only thing that bothers me is that there might be some weirdness related to specific peripherals (like the keyboard, for example). Unfortunately I only have PS/2 keyboards and use them with 5 pin DIN to PS/2 adapters. This usually works perfectly, but who knows? That's the thing with bugs, they tend to appear in certain specific conditions. 😀
Which is why I'd appreciate if someone else would try and see if they get the same behavior using their whole completely different setup.

Miphee wrote on 2020-11-30, 19:18:

Maybe the software is corrupted.

Unbelievable! You were actually right 😀 I feel so stupid now... Goes to show that the brain can easily be tricked. In fact, I was NOT using the same disk that I always use (it was a very similar one, but with lower capacity, because most of these motherboards don't support disk sizes above 32 GB). And, at some point in time, all disks were cloned from the same one - which, apparently, had a corrupt Prehistorik installation.
I actually ended up testing a 120 GB SSD (with a working Prehistorik install) on the Acorp 5TX29 (since this one does have a BIOS that supports disks up to 128 GB), and it worked like a charm. After that I copied this installation on all the other disks and... problem solved!

Thanks for the heads-up, Miphee!
So, false alarm, Prehistorik does work fine on 430TX 😁