First post, by ykot
I have just got a working 486 motherboard, but it has no identificable markings whatsoever. It seems to be based on SiS 496/497 chipset, has 3 PCI slots and 4 ISA slots. It also seems to have integrated IDE controller, but curiously, doesn't seem to have an identificable floppy connector, but I could be mistaken. For several hours I've went through known lists of motherboards watching pictures but can't find a match. A very distinctive feature of this motherboard are 4 DIP chips on a side of PCI slots, whereas most similar motherboards have SMD chips.
BIOS mentions this string on bottom: "03/31/95-SIS-496-497/a/b/2a4IBR21-00". On the back there are markings "tmf m21 94v-o", which don't seem to say anything.
Any help identifying this would be greatly appreciated.
Edit:
Thanks to all people who replied here, this has been identified as ATC/UNITRON U 6921, also known as "Terminator" board. Its configuration and jumpers are described here and here.
A useful guide for a similar board that has same CPU type jumpers with helpful pictures is in attachment below. I have also attached a working BIOS dump that came with this board.