Is the CPU on the iMac G5 upgradable? How is it mounted?

According to the respective Apple Developers Notes for the original, Ambient Light Sensor, and "iSight" iMac G5 models (each subsequently deleted), the processor in each is mounted directly to the motherboard. Consequently, it is not feasible to upgrade the processor in any iMac G5 model.

How do you upgrade the RAM in the iMac G5 models? How much RAM of what type do these systems support?

The original and Ambient Light Sensor iMac G5 models can be upgraded to a maximum of 2.0 GB of RAM by removing the pre-installed module and installing two 1.0 GB 400 MHz PC3200 DDR SDRAM DIMMs. Matching RAM modules should be installed for optimum performance. The Apple Support Site provides an extensive collection of instructions for upgrading the RAM and other internal components in these systems.

The iMac G5 "iSight" models have 512 MB of RAM soldered to the motherboard and formally can be upgraded to a maximum of 2.5 GB of RAM by installing one 2.0 GB 533 MHz PC2-4200 DDR2 SDRAM DIMM in the single DIMM slot (although a diligent reader was able to upgrade it to 4.5 GB reliably, see below for details). For the iMac G5 "iSight" models, the Apple Support Site also provides instructions on how to upgrade the RAM, but recommends that other components not be upgraded or replaced by the end-user.

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:

*RAM manufacturers and quality resellers that have tested their RAM with this specific Mac for reliability do not guarantee that this system can support more than 2.5 GB of memory. However, this iMac is so old that demand for upgrades is low. A diligent reader more recently discovered that it will work with a 4 GB Samsung 2Rx4 PC2-6400U-666 memory module, passes Memtest, and is properly recognized by the operating system.

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, it always is best to buy from a quality vendor that has tested their RAM with your Mac to ensure compatibility.

Site sponsor Other World Computing sells memory compatible with the original and Ambient Light Sensor iMac G5 models as well as the iMac G5 "iSight" systems.

How do you replace or upgrade the hard drive in the iMac G5 models?

The Apple Support Site provides an extensive collection of instructions for upgrading the Serial ATA (1.5Gb/s) hard drive in the original and "Ambient Light Sensor" iMac G5 models (as well as instructions to upgrade other internal components). Apple does not recommend that end-users attempt to upgrade the hard drive in the "iSight" iMac G5 models, but the always excellent XLR8YourMac provides unofficial instructions.

Site sponsor Other World Computing sells hard drives that are compatible with every iMac G5 model.

Does the iMac G5 have PCI slots or expansion bays?

No. The iMac G5 is designed to be simple, compact, and relatively inexpensive, and consequently, there is no internal expansion other than AirPort Extreme and Bluetooth (AirPort Extreme and Bluetooth 2.0+EDR were pre-installed starting on May 3, 2005 with the "Ambient Light Sensor" models).