First, make sure you have the latest BIOS (late 1995 if I remember correctly).

I assume you have the manual for the basic jumper settings, for a 5x86 you need to set the following:

1. JP5 3-4 & 5-6, RN2 & RN5 installed ("Intel, AMD")
2. JP8 2-3 ("Intel S Series, AMD Enhance Series")
3. JP9 Open ("AMD, UMC")
4. JP10 Closed ("Intel DX4 & AMD Enhance x 2") - this sets the 5x86 internal multiplier to x4
5. JP12 1-2 ("AMD Enhance WB") - this sets L1 cache to WB
6. JP13 Closed ("Others")
7. JP22 Open, JP23 1-2 ("AMD 3.3V, 5V") - CPU voltage detection, it will use 3.3V for the 5x86

The rest of the settings should be the usual (33MHz base clock, DX-type CPU). And remember to set L1 & L2 to WB in the BIOS for best performance.

Hm... something is weired... My mobo has the is revision 2.1
First the pins do not properly match: For instance JP8. Looking at the motherboard pin 2 can only either be closed with pin 1 or pin 4. Maybe they changed the pins between the revisions?
Also I found a bios in this thread: Ga-486AM/S jumper settings for Cyrix 5x86 100GP
But I cannot flash the chip with it. I think the chip and the bios image do not match? When I try to flash the award flasher says "The program file's part number does not match with your system!".
I also cannot flash it with my TL866CS programmer because the bios chip I have (SST PH29EE010) is not listed in the minipro programmer software.

Any ideas?

I usually just set the voltage, FSB and multi. It should just work.

Hm... I guess I need a bios update for the CPU to be properly recognized. It says I have an Am486DX4-S 100MHz cpu installed.
Any idea how I can flash the bios or does someone have a workign bios image?

Finally I managed to update the bios after trying a couple of different award flasher versions. The 5x86 is also recognized correctly now 😀

Does anyone know what the difference between revision 2.1 and 2.20 is? Is it worth getting the 2.20 revision?