Not long ago on local forum I have stumbled across a guy giving away AcerMate A1GX motherboard.

So I got my hands on it 😀 Good working condition. Unfortunately, it came without a riser card, but I think I can handle it.

Stats:
486CPU support up to 486DX4-100
Up to 256Kb L2 cache
36MB maximum RAM, 4MB built-in RAM
64KB SMRAM (?)
ALI M1429G chipset
CL-GD5430 video with 1Mb video memory extendable to 2MB (I have the needed memory chips currently working in another rig)
PS/2 mouse and keyboard
Coin cell lithium battery holder
Built-in 2 COM, LPT, 2IDE, FDC controller
Built-in tiny speaker

After a good cleaning, installing CPU, RAM and another 128Kb cache:

It currently has 486SX-25 CPU installed, but I have spare DX2-80 and 5x86-133ADW to adjust it's performance in case I need more horse power. Not that I really want to 😀

From the whole bunch of RAM I have, only several modules worked on it. I have managed to get 16Mb, which is more tham enough. The most capacity is reached with onboard RAM disabled.

Now, the creative part:
I got the board with the intention to build a very compact 486 with an external PSU. The case will be made of wood and plexiglas. I'm currently looking for a good 2-3 mm list of plexiglas for a reasonable price.

Here's the blueprint:

There'll be an opening in plexiglass over PSU and IDE connectors. The PSU cable and the IDE2SD adapter I ordered in a local radio store are going to be plugged through it for quick and easy access.

With no fans or HDDs inside the case, this is going to be the most silent PC ever 😀 After building the actual case, I think I might modify the PSU unit to work with passive cooling (this will require a massive heatsink though).

P.S. What is SMRAM for? I read the wiki page, but I don't get what it can be actually useful for.