I think I'll leave the system as it was without the NIC and XT-IDE. It's perfect now, exactly what I wanted. Thanks to you!!!! You were great!

Found this thread by googling, I have the same SBC, MikroMikko 4 m346.

Original BIOS says it's v2.06. Found MR BIOS from Re: How about a MR-BIOS ROM file repository?. Chipset is TACT83000. It worked somehow but
-the 32Kb cache stayed disabled, cachechk didn't see it at all (and yes, the bios was for the i385 cache controller)
-MR BIOS didn't see floppy and IDE ports on backplane at all, serial and printer ports were unvisible too

Damn, there was a lot of settings to tinker with... But I think I'll go with the original instead, maybe I'll try the v2.15 from this thread too.

I think this little SBC isn't bad at all... Pimped it a little:

-Ti486SXL2-40 @50MHz
-20Mb RAM
-4Gb CF-card
-Ethernet card with XTIDEBIOS
-CL-GD5426 ISA
-Gravis Ultrasound MAX
-Windows 95D Lite

It runs FastDoom fluently, Windows is little on the slow side but usable, Mod4Win works, and networking is great to have.