iMac G4 700mHz Flat Screen not Reading Internal Memory

Long story short: my G4 15" flat screen iMac suffered hard drive death in January 2008 (6 years old). I opened up the iMac and replaced the faulty hard drive with a compatible one that was 50 Gig (older one was 40 Gig). Put everything back, and sealed it correctly with thermal paste (per online instructions). Also purchased memory upgrade from originally installed 256 mg user access to 512 mg, which would have given me over 700 mg RAM with the internal 128 mg.

Now, for some reason, the iMac does NOT recognize the internal (hard to access) 128 mg, but only the 512 mg, and about 1 of every 5 times the computer is turned on, I get the three short tones and nothing, which means the computer does not have enough RAM to boot (not recognizing the 512 RAM in the user-accesible slot). I have re-seated the 512 Mg RAM chip twice as experimentation, and the computer works fine for a while (until the next shutdown, power-outtage, etc.).

Any thoughts? Should I replace the internal 128 mg chip with a new chip?

iMac Intell Duo Processor 2.0 GhZ, Mac OS X (10.2.x)

Posted on Nov 9, 2010 9:50 AM

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4 replies

Nov 9, 2010 11:13 AM in response to Jayworld

If it's recognizing the 128, then I would leave it for now and focus on the internal one.

Help me make sure I'm reading this correctly: So the computer sometimes sees the internal module? That sounds like a defective module, insufficient seating, or a dirty slot. Where did you buy it and what were the specs? Macs can't use just any RAM. However, if the module isn't Mac-happy, it should never show up, or be recognized as half its rated capacity. It would not be intermittent.

I won't buy Mac RAM from a brick-and-mortar superstore or from an auction site any more. Too many issues. I use two online vendors with excellent products and great prices. If you find you need to replace one or both modules, post back and I give you the links.

Nov 9, 2010 7:55 PM in response to Jayworld

With the minimum original factory capacity of RAM in the
hard-to-upgrade slot location, a standard 256MB chip in
all of the iMac G4 computers, it may be safe to assume
the computer can't use a 128MB chip at all in any slot.

(However the introductory 700MHz iMac G4 base model
did ship with a 128MB chip; it could be considered an
obsolete or damaged goods at this point. They stopped
shipping that low a chip in iMac G4s or upgraded them.
OS 9 could run circles around OS X with 128MB RAM.)

The upgrade chip capacities usually are 256, or 512; to 1024.

So, the factory chip capacity would be the likely minimum
the computer would be able to use. The answer would be
to get at least a 256MB or 512MB chip of good quality. And
the max upgrade would be 1024MB between both slots,
with each location requiring a different style of RAM to fit.

Hopefully the use of a non-standard RAM capacity won't have
harmed the computer's logic board or RAM slot connections.

For general mac specs, one can get a free download database
of hardware, software and some upgrade specs from MacTracker.
See http://mactracker.ca for the versions & current build available.

Good luck & happy computing! 🙂

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iMac G4 700mHz Flat Screen not Reading Internal Memory

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