> The R4k indigo, indy and indigo2 all use the same memory, I
> believe. The R3k, 4d/2x and 4d/3x machines used some wonderful
> proprietary sticks. I haven't a clue what older machines made use
> of.

correct. "modern" r4k systems use standard 72-pin 36-bit parity
simms. generally 70ns, though i've seen 80ns parts in use. (most older
cisco equipment (25xx, 4xxx, etc) uses these same parts.) where you
see 72-pin parts in a peecee, though, they're generally 32-bit, no
parity. 

indigo3k is a respin of the 4d/3x, with the memory controller asic
distributed across the simms. this was a speed hack. nobody liked it.

the VIP/30 and VIP/35 (essentially an indigo3k spun into a 6U VME
set for embedded applications) took really weird ram, they look like
short 72-pin parts. 64 pins? something like that. "i saw one once."

4d/2x used standard 30-pin simms in 4 banks of 4; the 1MB part was generic,
the 2MB part was special. undocumented special case: you could populate
bank D with generic 4MB simms, as long as they were all made by toshiba.

4d/2x0 boards (ip5) used 30-pin simms. later powerseries used special 80-pin
simms (2M or 8M) on a MC2 board.

"modern" hardware (ip19...ip31) uses special semi-proprietary dimms -- but
they're just ram, easy to make, unlike the indigo3k memory which required
that you buy some asics from sgi.