How do you upgrade the RAM in the iMac G4 models? How much RAM of what type do these systems support?

The iMac G4 models are unusual as they have two memory slots of different types -- one on the bottom of the logicboard that is easy to access -- and a second memory slot on the top of the logicboard that is difficult to access. Apple provides instructions to upgrade the memory in the bottom slot for both the original and Spring 2003 models -- which have 700 MHz or 800 MHz processors -- as well as the 17-Inch 1 GHz and USB 2.0 models -- which have 1 GHz or 1.25 GHz processors.

Specifics are provided on the specs page for each model, but for your convenience, details regarding compatible memory, number of memory slots, and maximum supported RAM also are provided below:

* Although Apple's original specifications stated that these models shipped with PC100 RAM, Apple later warned that "PC100 RAM is not to be used with iMac (Flat Panel) computers and may create performance and reliability issues".

† These models have one factory installed memory module in a 168-pin DIMM slot (the difficult to access top slot), and one 144-pin user-accessible SO-DIMM slot (the easy to access bottom slot).

†† These models have one factory installed memory module in a 184-pin DIMM slot (the difficult to access top slot), and one 200-pin user-accessible SO-DIMM slot (the easy to access bottom slot).

§ Apple officially supports 1 GB of RAM in these models, but unofficially these models support 2 GB of RAM.

Apple does not consider the top memory slot to be "user accessible" and consequently declines to provide applicable upgrade instructions. Consequently, EveryMac.com does not recommend that users attempt to upgrade the memory in the top slot themselves.

It is challenging to upgrade the memory in the top slot, and as such, users with limited experience upgrading computers would be wise to either just upgrade the memory in the bottom slot -- which is easy -- and make do with the "easy maximum" of memory or hire a professional. Even those with extensive experience upgrading systems might think twice about whether the "difficult" extra memory is really worth the trouble given the other limitations of the system.

Nevertheless, for the adventurous, the always excellent AccelerateYourMac has a detailed "take apart" guide for the iMac G4 that covers upgrading the memory in the top slot. The Italian Faqintosh also has very nice step-by-step instructions.

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 G4 models -- those with 700 MHz and 800 MHz processors and 1.0 GHz and 1.25 GHz processors -- as well as all other Macs.