I thought the layouts of the boards are identical, sorry for the confusion. I do have a stx2.

Check what is printed on your motherboard. In the pic I linked it looks like it says "DRAM & SDRAM MIX POSSIBLE" between the battery and the model number.

Also since it's a rare board, it'd be nice if you upload a good resolution pic. 😀

There are separate options for the SDRAM and EDORAM latency in the BIOS. Is it possible to use 64MB EDO sticks? Maybe someone has a running setup?
I played a bit with the EDO settings, according to everest 2.20 my read speed is 127MB/s, write is 65MB/s. Not bad right? Default was 107MB/s read and 60MB/s write

"Enhanced Write" made the PC stall during boot.

In the comparison table of everest it seems to be on par with a K6-2 500 now 🤣

I will try to get a good picture tomorrow 😀