I still have some motherboards left from hoarding that I can't/won't integrate into my Retro PC Gallery.
Today I decided to test them and sell them.

One of these boards is a Soyo SY-4SAW, it has visible acid damage.
SIMM1 is somewhat damaged. SIMM2 had bent pins.
It's a heavily used board.

I've spent some time until I managed to have a POST.
It was complaining of VGA... (BIOS beeps)... that was actually cache related. He did not like the cache memory chips it had.
Removed it, worked. Added them back, would not POST. Added different cache chips, worked.

So far so good.

My Am5x86-P75-S had a weird 150MHz clock and I could not get it to 133MHz.
Check the documentation and... well it's a forest of pins and jumpers but it looked right.
Decided to remove all and do a clean new jumpering based on the documentation found on retroweb.

Jumper setup done, POST: 133MHz!
Playing with CPU Bus or System Bus jumpers: 25,33,40,50MHz.
No voltage change, no other jumper change.
150MHz - POST.
160MHz - POST.
200MHz - POST! - The strangest thing is that it does this with the 40MHz bus setting.

The problem I have and why I can't test further.
This MB uses an old BIOS version: 10/14/95-SiS-496-497/A/B-2A4IBS29C-00
Am5x86-P75-S was released later.
Even on the stock 133MHz speed the system hangs at the floppy boot stage. I get "Starting MS-DOS..." and that is it. With Win98 boot disk I get nothing, just hangs right after reading the boot sector of the floppy.
With a 486 DX2-66 it boots fine, no issues.

I have two Am5x86-P75-S CPUs: ADW and ADZ. At stock 133MHz they behave similarly and both hang at boot.
Funny part, the CPU that POSTs at 200MHz is the ADW one. 😀
A different BIOS is on it's way: 07/03/96-SiS-496-497/A/B-2A4IBS29C-00

I am very curious if I can still POST at 200MHz.
If yes hopefully I can boot a floppy and do some tests, benchmarks and maybe even a few games.