If it is in it's genuine state, half-filled is most likely 1 MB
Either way, you can set up the extended RAM in the BIOS regardless of the real amount of RAM. Obviously, if it crashes when using the RAM, then you have set up too much.
I have posted the manual of the A2386sx here
http://www.toofiles.com/fr/oip/documents/pdf/bridgeboardmanual.html
