First post, by mpe
Sorted out my original issues. Looking for help with identifying vendor and model of this motherboard:
Intel 420EX (Aries) Socket 3.
There was only a handful of Aries board apart from Intel Ninja AFAIK and unlike most of them this one doesn't seem to be based on the reference design (namely 4 SIMM slots, PS/2 mouse onboard, >33 MHz support, etc.)
The only visible identifiers on the board are these:
150-0061-001 REV C
BIOS chip (AMI WinBios dated 07/25/1994)
They seem to be using S prefixes for jumpers (S1, S2, ...). Fortunately, everything seems to be well described on the board.