Third party memory for the 240s

[Jim Helman]

I too would be interested if anyone knows what plugs into a 4D/2x0
memory board.  SGI's memory prices appear to be seriously out of line
with the market ($48,000 list for 40MB).  Even with their educational
discount, it appears to be overpriced.  They also charge a quite a bit
to maintain it (approx. $2,500/year list for 40MB, at market prices I
could buy a lot of spare SIMMs for that).  Normally, we don't like
messing around with third party stuff, at least not on computers that
haven't been out long enough to establish their own reliability and
stability, but after seeing SGI's prices, it's worth a shot.

As I understand it, the only memory on the 4D/2x0 processor boards is
cache.  So when you get the minimum 8MB configuration, that memory is
on a separate board which can support up to 64MB of DRAMs.  The
question is what to plug in.  There are issues of speed, e.g. 80 or
100ns, and addressing mode, e.g. nibble burst mode.  And since the
memory system does error correction, it might not use usual 9x1mbit
SIMMS, which only have one bit extra for parity.

Anyone with a 4D/2x0 care to open it up and have a look?  Any
information would be much appreciated.

Jim Helman
Department of Applied Physics			P.O. Box 10494
Stanford University				Stanford, CA 94309
(jim at thrush.stanford.edu) 			(415) 723-4940