12 Nov
2006
12 Nov
'06
4:20 p.m.
I heard a strange rumor to the effect that the PC/XT
286 incorporated a "real" 5170 mobo. I didn't really
believe it when I heard it, but besides, some full
size clone AT cased couldn't take a real 5170 mobo,
how could the (essentially an XT case I guess) take one?
No it doesn't, for the reason you've suggested. A 5170 mainboard will not
fit in an XT case.
The XT-286 mainboard is electrically quite similar to the AT (5170)
mainboard, but there are differences. One obvious difference is the RAM
-- the AT mainboard can take a maximum of 512k (either in 256K*1 chips in
later versions or some odd IBM 128K*1 devices that are actually 2 64K*1
chips with strange pinouts piggybacked in earlier versions). The XT-286
board is designed to hold 640K as 2 256K*9 simms, 4 64K*4 chips and
2 64K*1 chips (parity on that last 128K).
There's also a problem with some adapter cards being too tall to fit in
the XT case. For example only ther later version of the hard/floppy disk
controller will fit.
-tony