In theory, you can mix edo and ftp simms as an installed pair in a 486
motherboard design. On a Pentium motherboard, a pair or simms have to match
but you can install two different matched pairs. Pentiums have double the
memory data bus width of a 486, so 72 pin simms (edo or ftp) were installed
in pairs to fill the entire bus, and consequently the pair had to be the
same size. In practice, you have to follow the manual, probably because of
cost cutting in the design of the board.  When the manual doesn't explicitly
prohibit it, I have sometimes found weird simm combinations that worked.
Back to the main thread, be aware of the difference between single sided 256
meg sdram and other types.  Your board may require a particular model of
ram.  Check out www.Kingston.com for its memory configurator.
Tom Turak

-----Original Message-----
From: Mark Rode [mailto:[log in to unmask]]
Sent: Tuesday, July 10, 2001 4:01 PM

EDO (Extended Data Out)  SIMMs require matched SIMMS sets, and Pentium
class boards that supported EDO often required matched sets of whatever
SIMMs were being used...i.e. FPM or EDO. However FPM (Fast Page Mode) never
required in itself, matched sets nor did any 486 using FPM 72 PIN SIMMs. In
fact I would guess that most 486s with 72 pin SIMMs were sold with a single
4 meg SIMM. Of course 30 pin SIMMs which were common in early 486 boards
required matched sets of four.

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