Yesterday I've been toying around with some industrial boards. Among them the Mitac MSC-242 SBC with Intel DX2 and 8MB ram.
Had a thread about it earlier:
Mitac MSC-242 Isa motherboard manual / jumper settings?

I thought I'd be fun to upgrade the ram to 64MB and see what it would do.

First tests confirmed: EDO is a no go. Fpm is the way.

Second test: 32MB fpm module: all ok in BIOS post, himem and speedsys.

Third test: 2x32MB fpm modules: BIOS post only counts up to 48MB. Himem and speedsys are ok with 48MB. No 64MB though. Also not when the modules are witched.

Fourth test: the second 32MB module alone: again 32MB ok.

That's not how I want it, so here comes 2x8MB fpm. Bios recognise 12MB total (??), Himem and speedsys are ok with 12MB but no 16MB. Both modules go up to 8MB when seated alone.

One 16MB module: OK.

2x 4MB modules: all is ok with 8MB total even with different pairs (60/70/80ns)

So if I put in two modules larger than 4MB, the second one is halved in capacity.
If I put in only one (no matter which slot) it is working like it should.

What could this be?