64 pin SIMM (Mac IIFX) Specs?
trag at io.com
Wed Aug 31 13:28:41 CDT 2005
I am looking for specifications for the 64 pin SIMMs used in the
Macintosh IIFX and one or two of the LaserWriters (IINT, IINTX?). I
have the pinout from the "Guide to the Macintosh Family Hardware" but
could use the physical dimensions, i.e. an engineering drawing. Any
special electronic considerations would be nice to know too. I'm
thinking about running off a few homebrew boards.
One of Apple's old Tech Notes states, "The IIfx has 64-pin SIMMs,
which are different from previous Macintosh models. Developers can
request mechanical drawings and electrical specifications of the IIfx
RAM SIMM modules from DTS. Please send the request with a mailing
address and include the words "IIfx SIMM information request" in the
title of the electronic mail request or letter to facilitate
But since that note was last updated in 1991, I'm guessing that
wouldn't work any more. But if one of you sent off for that
information way back when, I would love to see it.
My main concern is that the pinout lists a separate data pin for data
in and data out. So even though they are eight bit SIMMs, there is
a Data In [0:7] and Data Out [0:7] in the pin out. It's possible,
perhaps likely, that these are simply tied together, but it would be
nice to see some confirmation. The chips I've identified on IIfx
SIMMs don't appear to be dual ported and I don't see any extra
circuitry on the SIMM that could be making an adaptation, but I'm
working from JPEGs so far. If this looks feasible I'll actually
spring for a IIfx and a few SIMMs to work from.
On the other hand, if the SIMMs require some rare dual data ported
DRAM chips, then I'll drop the idea.
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