Installing third party 4 meg simms in an IRIS 4D/20

[Fisher]

In article <33517 at usc.edu> walker at sulu.usc.edu (Walker J. Seestedt) writes:

|>Recently, in the interest of getting more memory into our SGI Personal
|>IRIS 4D/20, we have purchased some third party memory from Kingston
|>Technology Corp.  Since the existing 8 meg is in the form of 1 meg
|>simms, and the Kingston memory is in the form of 4 meg simms, we must
|>discard the old memory for the new.  We have 24 meg that we want to
|>install, however no matter what configuration I place the simms the machine
|>refuses to boot (or even go through power on diagnostics.)  I have tried
|>nearly every memory configuration I can think of, but to no avail.  Kingston
|>doesn't really know what configuration they should be and told me to try
|>different combinations.  Big help.  So, if any of you guru's out there
|>have managed to get 4 meg simms configured into a Personal Iris, PLEASE
|>let me know how they should go in!

You have to add in four SIMMs at a time.  With 4Mb SIMMs, you can have
16Mb, 32Mb, 48Mb, and 64Mb, but not 24Mb.

Your 8Mb 1 Meg SIMMs originally looked like this:

     ------   ------
     ------   ------
     xxxxxx   xxxxxx
     xxxxxx   xxxxxx

     ------   ------
     ------   ------
     xxxxxx   xxxxxx
     xxxxxx   xxxxxx

You would use the same layout for 32Mb using 4 meg SIMMS.  For 16Mb
using 4 meg SIMMs:

     ------   ------
     ------   ------
     ------   ------
     xxxxxx   xxxxxx

     ------   ------
     ------   ------
     ------   ------
     xxxxxx   xxxxxx

And for 48Mb, you would use:

     ------   ------
     xxxxxx   xxxxxx
     xxxxxx   xxxxxx
     xxxxxx   xxxxxx

     ------   ------
     xxxxxx   xxxxxx
     xxxxxx   xxxxxx
     xxxxxx   xxxxxx

BTW, I think I remember hearing that the early 4D-20's wouldn't work
with the 4 meg SIMMs.  Anyone remember?

-steve