A Guide to Upgrading Memory
This document provides information on installing and removing SIMMs in Power
Macintosh computers, specifically the Power Macintosh 7100. Due to the layout
of the internal components of the 7100, it is one of the most difficult machines
to be RAM-upgraded. I discovered this when I tried it myself! For this reason,
I recommend that you have a professional install your RAM.
However, I am not a professional. But if you are going to
attempt it yourself, it really helps to have the right information--I wish I had
it when I started!
SIMMs for the 7100
Accessing the Slots
The Power Macintosh 7100 has 8 Megabytes of RAM soldered to the motherboard, and
4 slots for adding additional RAM, which must be in the form of 72-pin,
non-parity SIMMs of 80ns or faster (70 or 60ns). In addition, SIMMs must be
installed in pairs, where each pair consists of 2 identical SIMMs of 4, 8, 16,
or 32 Megabytes. Separate pairs need not be identical. So the maximum memory
configuration on the 7100 is 2 X (2 X 32 Mb) + 8 Mb = 136 Mb. Any configuration
over 8 Megabytes (not Virtual Memory) indicates that 2 or 4 of the SIMM slots
are in use.
In regards to purchasing RAM, the
RAM-specialty mail-order vendors seem to have the best prices. I am the
satisfied customer of RamJet. Check
RamWatch for the
The most crucial aspect of installing RAM modules is preventing electric
discharges, such as those caused by static electricity. This applies to the
chips themselves and anything else in the case or on the motherboard. Don't
stand on carpet, and if possible use an anti-static mat to stand on and an
anti-static bracelet to wear.
Power down the computer along with all peripherals. I have read that it takes a
while for some components to fully discharge, so you might want to let it sit
like this overnight. Leave the main box plugged in to a grounded socket, so
that you can use the power supply as a ground for yourself if you don't have an
anti-static bracelet. With a flathead screwdriver, unscrew the large screw at
the top of the rear panel of the 7100's case. It doesn't come out, you just
have to loosen it all the way. Place your palms on the sides of the case and,
pressing inward, pull the case forward a few inches and then lift directly
upwards. Place the cover aside.
Now comes the hard part, what makes the 7100 one of the hardest machines to add
RAM to. The SIMM slots are on the motherboard, beneath the CD-ROM drive. The
platform on which the drives and power supply are mounted is screwed into the
case at two places: to the left of the hard drive and to the right of the CD-ROM
drive. Unscrew these 2. The rear of this platform simply rests in the back
panel of the case. What you have to do to access the slots is to lift up the
platform in the front, so you can fit your hands underneath the CD-ROM drive. I
needed a friend to help me out here. It also helps to remove the power supply,
though some have claimed it isn't necessary. To remove the power supply, take
out the plastic clip that lays across it on top, and unplug the cord from the
rear of the case if you haven't already. If you look beneath the power supply,
you will see the white plug where it attaches to the motherboard. You might
have to loosen this a bit by prying with an insulated material. Then lift the
power supply straight up.
When handling the SIMMs, make sure you are properly grounded. Each SIMM slot
has a clip on each end that holds the SIMM in place. If you are removing SIMMs,
the clips have to be pushed away from the SIMM, and then the SIMM can be
removed. To install SIMMs, push out the clips, then set the SIMM module into
place at a slight angle. Wiggle it back and forth a little bit to make it seat
properly. Push it into the straight up position and make sure the clips have
also seated properly. Remember that 2 identical SIMMs must be installed
You've done it! Now all you have to is put back the power supply, making sure
the plug seats properly into the motherboard, replace the clip, the 2 front
screws, the cover, and the back screw that secures the cover. Once you have
plugged everything back in, start up and check the About This Macintosh... item
in the Apple Menu to make sure the system recognizes your new memory.
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This page was last modified on 10/31/99; 9:10:38 PM.