[rescue] SGI Challenge Memory

[Sheldon T. Hall]

Folks-

I have an SGI Challenge L with three MC3 memory boards; the boards are fully
populated with 16-MB SIMMs.  That's 32x3=96 SIMMs for a total of 1.5 GB.

I have another MC3 board and 12 more SIMMs I'd like to install.

At issue is the memory interleaving and SIMM installation, and I'd like some
advice.

According to http://www.impediment.com/kingston/odata/sil005.htm ...

[quote]
Each memory board consists of 8 banks, with the sockets physically arranged
in blocks of four.

2-way interleaving can be accomplished by filling corresponding banks (banks
A & B, C & D etc.) on one board.

4-way interleaving can be accomplished by filling corresponding banks across
two boards.

8-way interleaving can be accomplished by filling corresponding banks across
four boards.

SGI's documentation recommends taking advantage of interleaving capabilities
instead of filling all the banks on one memory board when the system
contains multiple memory boards.

Each system can support up to 4 memory boards.
[unquote]

OK, I've got 108 SIMMs, but if I want to use the 4-board interleaving, it
looks to me like I have to have 16 SIMMs per "interleave set", i.e. 4 per
bank on each of 4 boards.  If that's so (and I'd love confirmation of my
understanding), then it looks like the additional 12 SIMMs I have won't be
of use.

It also seems like having three MC3 boards in the machine might be mucking
up the interleaving scheme.

Should I re-deploy the SIMMs now on the three boards and spread 'em across 4
boards to get the interleaving, or just put the 12 extra SIMMs on the fourth
board, put the board in the machine, and not obsess about squeezing the last
bit of performance out of the thing?

-Shel


--
Sheldon T. Hall
shel at cmhc.com
206-780-7971 (CMHC)
206-842-2858 (Home)