I've got this sorry looking board earlier this year as I was looking for an ISA SBC. It's a popular (I think - they are still manufactured/sold new) industrial computer. It has an Am5x86-P75 with an ALI 486 chipset (M1487 + M1489). I'm aiming to use it with one of the ISA risers laying around to build an ISA system.

(ignore the graphics card, unrelated. This is an old photo)

It was pretty beaten up as the scrap seller already managed to remove the BIOS chip messing up several traces in the process... I managed to repair them.

I confirmed it works in my PICMG backplane with my "test bios" installed (it would show bus activity but hang, no beeps at all). Having no luck finding the BIOS for it (at that point I haven't even noticed the part number marking) I just put it in storage to wait for better times. Some time ago a friend identified it as a "Nupro 406 Rev:A3" (it literally says that on the edge, how did i miss that is beyond me) and I started to search for it's BIOS.

I also figured out the power cable and powered it up again (this time with no backplane)

The power input pinout is as follows (the pins are connected directly to the fingers on the ISA edge connector):

1power header J1
21   +5V
32   +12V
43   -12V
54   GND
65   GND
76   -5V
87   +12V
98   +5V
10pin 1 towards edge. Connector pitch 100 mils. 

I'm positive all the connections are intact, I tested them on continuity. All address and data pins of the ROM have a connections to the M1487 (I think they are all correctly wired, it was obvious how the traces go, but I have no pinout of the M1487 so I can't fully confirm). I tried several bioses for 486-en with this chipset but so far none of them made it beep or give any signs of life. Currently I have it running my own "BIOS" which is just a ROM image filled with a bunch of NOPs and a jump back to the entry point (F000:FFF0).

I'm scoping the address and data pins of the flash and I can see that it's executing the code correctly, although the address bus is full of glitches which I don't like, I'm not sure if this is an error. They seem to happen only when OE# is high..

It seems to be fully working and just needing the correct ROM image. The original board seems to be using an Award BIOS an an 39SF010 flash. Maybe someone has an image for it (or for a similar unit)? Maybe someone has the board and could dump it for the greater good 😀 ?