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iMac G3 Q&A - Updated February 22, 2009
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How do you upgrade the RAM in the iMac G3 models? How much RAM of what type do these systems support?
Unlike upgrading the hard drive and optical drive, Apple considers the RAM in the iMac G3 models to be a "customer-installable part" and provides instructions for the tray-loading iMac G3 models (those with 233 MHz, 266 MHz or 333 MHz processors) -- in two parts -- and the slot-loading iMac G3 models (350+ MHz) on the Apple Support Site.
With a quick glance at these instructions, it becomes readily apparent that upgrading the RAM in the tray-loading models is quite the chore -- effectively requiring one to disassemble the computer (and once you've gone that far it's not that much more work to replace the hard drive and optical drive) -- and upgrading the RAM in the slot-loading models is delightfully simple -- merely requiring one to twist a coin in a slot to "unlock" a small door and quickly access the memory banks.
Memory specifics are provided on the specs page for each model, but for your convenience, details regarding compatible memory and maximum supported RAM -- all iMac G3 models have two slots -- also are provided below:
iMac G3 | RAM Type | Max |
PC66 SDRAM | 128 MB* | |
PC66 SDRAM | 128 MB** | |
PC66 SDRAM | 128 MB** | |
PC100 SDRAM§ | 512 MB† | |
PC100 SDRAM§ | 512 MB† | |
PC100 SDRAM§ | 512 MB† | |
PC100 SDRAM§ | 1.0 GB | |
PC100 SDRAM§ | 1.0 GB | |
PC100 SDRAM§ | 1.0 GB | |
PC100 SDRAM§ | 1.0 GB | |
PC100 SDRAM§ | 1.0 GB | |
PC100 SDRAM§ | 1.0 GB | |
PC100 SDRAM§ | 1.0 GB | |
PC100 SDRAM§ | 1.0 GB | |
PC100 SDRAM§ | 1.0 GB | |
PC100 SDRAM§ | 1.0 GB |
* This is the maximum RAM officially supported by Apple. The "revision A" model "unofficially" can support a maximum of 384 MB of memory (one 128 MB and one 256 MB module) and the "revision B" model can use a maximum of 512 MB of memory (two 256 MB modules).
** This is the maximum RAM officially supported by Apple. "Unofficially" these models can support 512 MB of RAM (two 256 MB modules).
† This is the maximum RAM officially supported by Apple. "Unofficially" these models can support 1.0 GB of RAM (two 512 MB modules).
§ PC133 memory is backwards compatible with PC100 memory and may be easier to find.
Helpful individuals also have written their own step-by-step guides for the tray-loading (now offline) and slot-loading iMac G3 models that cover memory as well as other internal upgrades. You may find some of the "unofficial" tips useful.
Please note that just because RAM meets the minimum listed criteria does not mean that it will necessarily function as intended in a particular Mac. When buying memory, be sure to buy from a quality vendor that has tested their RAM with your Mac to ensure compatibility.
Site sponsor Other World Computing sells memory for all iMac G3 models -- tray-loading and slot-loading -- as well as all other Macs.
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