riscy
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SIMMs

To: riscy@pyramid.com
Subject: SIMMs
From: Jerry Callen <jcallen@Think.COM>
Date: Thu, 15 Jul 93 16:45:29 EDT
In-reply-to: Keith Rohrer's message of Thu, 15 Jul 1993 15:20:43 -0600 (CDT) <9307152020.AA23060@fncrdh.fnal.gov>
Reply-to: riscy@pyramid.com
Sender: owner-riscy@pyramid.com
   From: rohrer@fncrd8.fnal.gov (Keith Rohrer)
   Date: Thu, 15 Jul 1993 15:20:43 -0600 (CDT)

   > --- Andreas Busse wrote:
   > This is all more or less true. 3-chip x9 SIMMs have only few more chips 
than
   > x36 SIMMs. The discussion what SIMMs we should use had no technical reason,
   > just a practical. RAMs are going to be more expensive, so it would be
   > desirable for most of us to use the SIMMs we already *have*, and these are
   > 1Mx9 and 4Mx9 SIMMs, with a few exceptions.
   > --- end of quoted material ---
   > I think it makes the most sense to design for what we *will be* able to 
buy,
   > not what we have now.  Building a "junk box" computer may be fun, but is a

   You mean, buy the motherboard, let it sit in a closet until the following
   summer when I can afford the memory?  Depending on how layout goes, it might
   be good to have a daughtercard with (full-speed) simm sockets of x36 or x9,
   depending on the card or some of each.  If we have enough VLSI chips for
   the real work, board space may not be a problem, but beware also creeping
   featurism and overflowing the board with all the connectors for the things
   the wonder-chips will also do...

At some point this group is going to have to decide just what
price/feature/performance trade-offs it wants to make. Some people insist
that the board be able to have at least 64MB of memory. From a reliability
perspective, using x9 SIMMs to get there is wacky. It also eats more board
space for sockets and (probably) more drivers. The comment that 3 chip x9
SIMMs don't have more chips that x36 SIMMs doesn't wash; if you have OLD
SIMMs that you want to reuse, I'll bet they are NOT 3 chip SIMMs. Are they?

I have all sorts of stuff in my junkbox (AKA "my old system"). I don't want
to cripple any NEW system just to shave a few bucks off (which, because of
board space, etc, it might not do anyway).

   > SIMM "shape" is tending from the older x8 and x9 SIMMs to x32, x33, x36, 
and
   > x40 SIMMs.  Some of this is due to Wang Labs reaching out from the grave to
   > try to strangle other companies.  Some is due to benefits of the x32ish
   > shape.
   Hmmm...more expensive, and yet you need to replace it in larger hunks if/when
   it goes bad.  Sounds superior to me...  /*sarcasm off*/

See above. Fewer connections == more reliable.

Why is everyone so hung up on DRAM chip reliability anyway? I wonder how
many SIMM failures are bad chips vs. failed connections?

-- Jerry Callen
   jcallen@world.std.com           (preferred)
   jcallen@think.com               (OK, too)
   {uunet,harvard}!think!jcallen   (if you must)

 

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