RS600 3rd party Memory

[John D. McCalpin]

> On 5 Mar 91 11:21:39 GMT, havaki at csi.forth.gr (Popi Havaki) said:

Popi> We are going to order two RS6000/320 workstation with 8MB ram
Popi> each from IBM.  I have found 3rD party memory for this machine
Popi> from Castle Rock inc in 16MB upgrade kit . Does anyone have
Popi> experience buying memory from this company? Does anyone know if
Popi> we will have problem to increase RS6000 memory from 8MB to 24MB
Popi> adding the upgrade kit mentioned above ?  I will appreciate any
Popi> comments about adding third party memory on RS6000/320 machine.

I guess that it is about time to put together a frequently asked
questions list for the IBM RS/6000's.  Here is my contribution:

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Third-Party Memory:

Memory modules (SIMMs) for the IBM RS/6000 machines are available from
a number of vendors. (See list below).  As of this time, memory
*boards* are not available from 3rd parties and are not expected to be
produced any time soon.

Because of the details of the high-performance memory bus on the
RS/6000 machines, memory can only be added in specific configurations:

(1) For the 20 MHz machines (Models 320 and 520), memory must be
configured as boards populated with all 8 SIMMs.  These SIMMs can be
1MB, 2MB, or 4MB each -- yielding a total of 8MB, 16MB, or 32MB per
memory board.  

Note that the 8MB SIMMs *will not work* on most machines, as they
require a new revision of the memory board that may not even be
shipping yet.  My most recent information says that IBM intends to
ship this board populated with either 32MB or 64MB of RAM.  If you buy
an 8MB or 16MB board, you will likely get the older board which cannot
use the 8MB SIMMs.

(2) For the 25 MHz machines (Models 530, 730, 930), memory must be
configured in *pairs* of *identical* boards.  All other comments above
apply. 

(3) For the 30 MHz machines (Model 540), special memory modules and
boards are used.  I do not know of any third-party sources for these
SIMMs.  Reports suggest that the Model 540 may be retrofitted in the 
future to use standard memory.  Ask your IBM salescritter for more
info.

(4) For the 41 MHz machines (Model 550), I do not have any info.  I
have heard that the machine uses standard 5 volt SIMMs, but I do not
know if the speed requirements are the same as for the slower
machines.   I have heard rumour that the boards must be in identical
groups of 4, but I have no confirmation on this.

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Partial List of Vendors
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I have personally tested memory from the following two vendors.  Both
are shipping now:

(1) Impediment, (617) 837-8877, Alex Sunguroff.  Shipping 4 MB SIMMs.
    I have 32MB of this memory on a board in my Model 320.

(2) Clearpoint 1-800-CLE-ARPT.  Shipping 2 MB and 4 MB SIMMs.
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--
John D. McCalpin			mccalpin at perelandra.cms.udel.edu
Assistant Professor			mccalpin at brahms.udel.edu
College of Marine Studies, U. Del.	J.MCCALPIN/OMNET