Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!apple!dwells
From: dwells@Apple.COM (Dave Wells)
Newsgroups: comp.sys.mac
Subject: Re: Memory Questions
Message-ID: <32464@apple.Apple.COM>
Date: 16 Jun 89 01:30:26 GMT
References: <2289@amelia.nas.nasa.gov>
Distribution: usa
Organization: Apple Computer Inc, Cupertino, CA
Lines: 52

In article <2289@amelia.nas.nasa.gov> venkatap@amelia.nas.nasa.gov (Ethiraj Venkatapathy) writes:
>    Will some kind soul on this net explain the following terms:
>       1) DIP SIMM
>       2) SOJ SIMM
>       3) Surface Mount SIMM
>    Which of these is better and at what speeds (in ns)? I need this
>    information specifically for a MacII/IIx/IIcx. Please post or

DIP = Dual Inline Package
SOJ = Small Outline, J-mount lead

Surface mount is the technology of mounting components _onto_ a circuit board
instead of through.  J-mount leads are designed with this purpose in mind.
They're placed on the prepared circuit board with the 'J's sitting on contact
points and are then attached using various soldering/cementing methods.
The idea is simpler automated assembly and board design simplification, etc.

Dual Inline Package conponents use the original "drill a hole and poke the
pins through" idea.  You've probably seen them.  It's just a chip, or what-
ever component, with a row of pins pointing down from each side.  Poke 'em
through holes in the circuit board and solder.  Their package (case) is
larger than that of SOJ components, and this accounts for the restrictions
on which machines they work best in.  Of course, they're nicer than SOJ
components when it comes to wire-wrap!  ;-)

A Surface Mount SIMM is just a Single Inline Memory Module that uses some
form of surface mount technology to attach the RAM.  Beware pseudo-surface
mount in the form of DIPs with the pins chopped off at the knees!  They still
use the larger package DIP ICs and won't fit everywhere.

You may also encounter SIMMs using PLCC RAM.  (that's Plastic Leaded Chip
Carrier)  They have a slightly smaller package than the DIP, but are
essentially the same as far as fitting in Mac's is concerned.

For any of the Mac II family you can use any of this RAM so long as it's
rated at 120ns or faster (smaller # is faster).  The Mac II's have plenty of
room so there's really no best _unless_ you plan on moving the RAM to a
Plus or SE later.  (who knows?  When we all use 4MB SIMMs in our II's we'll
have to find a use for all those 1MB SIMMs.)  If one must be better than
the other, real surface mount is generally considered to be better because of
its smaller size and the resulting increase in applicability.


-Dave

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           Dave Wells, Apple Computer, Inc.  MS: 37-O  (408) 974-5515
          Mail: dwells@apple.com or AppleLink d.wells or GEnie D.WELLS
 These opinions may be nothing more than the ramblings of a fatigued tinkerer
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 There's one big difference between genius and stupidity.  Genius has limits.
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