Received these 2 beauties today:
first 386 motherboard

a 386sx-16 with 1MB built-in and slots for another max 4x1MB chips. Has a custom DTK BIOS-like setup program, but it's not a run-of-the-mill BIOS. It's by DTK/Datatek and has some advanced features. For instance there's a special section for setting the NEAT chipset which can apparently map XMS into EMS without any external utility. 😀
I've hit an obstacle though: it doesn't seem to recognize any of the floppy controllers I have, and it won't boot if it doesn't find one, even if both floppies are set in the setup program to "none" Still investigating...
I've replaced the battery already. There was a bit of corrosion on the battery's negative terminal, but it looks like it didn't reach the motherboard. No damage anywhere.
second 386 motherboard

I expected this one to just work, but it doesn't. When I power it on, the keyboard LEDs flash briefly then turn off. No video out at all. I only tested with one video card though, I may go back and test again with others. Tried several of the ISA slots, same result. I don't know what the large brown connector is for. I assume the connector right next to the CPU is used for some sort of memory extension card which I don't have. But why? It already has 8 30-pin slots for memory, more than enough for extra RAM. The board is apparently made by AMI (the BIOS company).
I can't find it in TH99, this is model 386XT series-17, the only AMI 386XT in TH99 is series-6 which has a completely different layout. I can't find a battery, or a connector for one, anywhere on the motherboard. No DS or equivalent chip either. Perhaps it would be on the expansion card, or on whatever plugged into the brown connector?
If anything, the layout is similar to this AMI 386SX motherboard: http://arvutimuuseum.ee/th99/m/A-B/30911.htm However this one has a coin battery pictured, and connector J2 for an external battery and J1 to select internal/external battery. My motherboard has none of the above.
I/O, I/O,
It's off to disk I go,
With a bit and a byte
And a read and a write,
I/O, I/O