Subject: SIMM sockets...

From: Pat Mackinlay <[email-masked]>
Date: Mon, 28 Jun 1993 16:00:55 +0800 (WST)

Neil, are you still planning on using 32 SIMM sockets? I've been looking,
and I just can't see how you plan to fit that many on the board if you
plan to do an ISA bus as well. 32 sounds a little excessive in any case.
I think we might do better to think about 8, possibly 16. More than 4
sockets is going to mean external memory drivers anyhow, so there's no
real difference between 8 and 16 apart from board space. Perhaps we can
allow 16M SIMMS to be used? With 8 x 16M SIMMS, we get the same 128M
maximum, perfectly reasonable from my point of view <grin>.

Pat -- "There's only one thing left to do Mama, I got to ding a ding dang
	my dang a long ling long" (Jesus Built My Hotrod -- Ministry)
GCS d* -p+ c++ l++ m--- s+/- !g w- t- r

---

From: [email-masked] (Steven D. Ligett)
Date: 28 Jun 93 09:03:03 EDT

--- Pat Mackinlay wrote:
Neil, are you still planning on using 32 SIMM sockets? I've been looking, and
I just can't see how you plan to fit that many on the board if you plan to do
an ISA bus as well.... Perhaps we can allow 16M SIMMS to be used? With 8 x
16M SIMMS, we get the same 128M maximum, perfectly reasonable from my point
of view <grin>.
--- end of quoted material ---
I think that the problem is the plan to use the glue chip that only supports
1MB and 4MB chips.  (If I understand what's been said about the 7370 (?).)  
A typically shortsighted chip design, I'd say.

Let's take a quick look at the costs of the board and sockets for these 32
SIMMs.  Ignore the space and cost of the memory drivers that will be needed.

For a 6-layer board, $1.50 per square inch for the PCB.  Each socket is about
0.3" by 4".

board cost = $1.50 * 32 * 0.3" * 4" = $57.60  
just for the board space.

socket cost = $1.95 * 32 = $62.40
for the sockets.

$120 to put 32 empty SIMM sockets on the board.  Assume that I'm
misremembering the socket cost, and that we go with a 4-layer board, and that
goes down to $100.  Still too much.