Hello everyone,

I recently got my hands on a very nice Zida 4DPS ver 2.1 board with 16 MB FPM RAM (I tried a few EDO sticks but they either don't work at all, or they cause extreme instability).
Anyway, the current config is the following:

MB: Zida 4DPS ver 2.1
CPU: AMD AM5x86-P75 133 MHz
RAM: 16 MB FPM
VGA: Cirrus Logic CL-GD5430 1 MB
Sound: ESS AudioDrive ES1869

So far I'm extremely pleased with the build, it's very stable and quite fast (65 FPS in 3DBench 1.0c)
The only problem is that, I was hoping to also be able to quickly slow the system down to 386 SX level (by using the Turbo switch). However, this is not the case. The turbo switch only has a 25% performance impact (the 3DBench 1.0c score decreases from 65 FPS, down to 52 FPS)

I tried various BIOS revisions, including 1.72F, 4.00A (found here: Zida 4dps v2.11 updated 400A bios) and 5.00A (found here: Re: Zida 4DPS (Tomatoboard) Socket 4 SiS PS/2 mouse not working)
Unfortunately, none of these BIOS revision/patches seems to have any effect on the slowdown capabilities with an AM5x86-P75 CPU.
The only way in which I can slow it down is by manually disabling the CPU internal cache in the BIOS (which will give me a score of 10 FPS in 3DBench 1.0c).

Does anybody know what I could try? I'm guessing that I might have better luck with a different CPU, but I would prefer to keep this one to have a "late era 486 machine".
I also have an Intel 486 DX2-66 CPU, but I'm saving that one for a more "period correct" machine, with VLB slots.