That raised multi-pin header was another version of cache memory setup. Doubt you could ever find another of that vintage, being more than 20 years old. Acer, Asus, AST and a few other brands did use that design feature. Some models did have what looked like a 16-bit ISA slot, but had 3 slot sectors, for a dedicated memory expansion card.. up to 16 MB.
Possibly a reference to what you have can be found from this site..
http://stason.org/TULARC/pc/motherboards/Another reference site is
http://www.elhvb.com/ .
Those 12 DIPP chips nearby show a "-80" on the top line, indicating an 80 µs speed. The "TI " to the left indicates made by Texas Instruments. Second line is the model/version and capacity of the chip. Third line is manufactured date. That is your on0board 4 MB system memory. Note the "1024" in the second line, indicating a 1 MB capacity. But those older cache (and main memory) designs had separate odd/even register banks. So you needed double the required amount, plus a 'tag' memory amount for parity. "Odd" bits of memory are 1, 3, 5, 7 and so on. "Even" bits of memory are 0, 2, 4, 6, and so on. Yes, "zero" is a physical statement with data info!