Repairing and upgrading an iMac G3 (Part 1)

November 4th 2018, 22:23 | Written by Konstantin Koll

I've got an old iMac G3 as birthday present back in August, and it's now officially my side project to repair and upgrade this classic piece of technology before selling it on.

I was pretty speechless when my friends showed up to my birthday party with a Blueberry iMac G3 with 384 MB of RAM and a 6 GB harddrive. It turned out that the device was functional, albeit in terrible condition: dirty (including stains of white wall paint on the case), a missing mouse, a filthy keyboard in the wrong color (Lime), and a very noisy harddrive. To make things even worse, the iMac is completely unusable as the previous owner did not reset the login password. Fair enough, it was sold for a bargain price of only 20 Euros.

I really have no use for such an old iMac, so I want to sell it for profit after repairing and upgrading it. I gave the case a thorough cleaning from the outside (for now), and also dismantled the keyboard for cleaning. I'm waiting for an original keyboard and mouse in Blueberry to arrive, then I will put the Lime keyboard up for sale on eBay.

RAM upgrade

The easiest hardware upgrade for an iMac is replacing the RAM—it's even considered user-servicable by Apple. There were two 128 MB SD-RAM bars installed. I booted into Open Firmware by pressing Ctrl, Alt, O and F simultaneously at startup. The command dev /memory@() .properties reveals detailed information about the installed RAM. Both modules were of 128 MB size (08000000), but with different timings (PC100-222S and PC100-322S). This means that the entire RAM got slowed down by the slower module.

I purchased two similar 256 MB modules on eBay (PC133 are much easier to obtain and compatible to PC100). Installing those modules was very easy, as the RAM slots are accessible by a plastic cover on the iMac's bottom.

The iMac boots fine with the newly doubled RAM, and Open Firmware shows nearly identical RAM properties with PC100-222S timing for both modules.


The next step is replacing the dying harddrive. G3 iMacs can address up to 128 GB, so I purchased a 32 GB SSD. It's very hard to replace the harddrive, I will have to take the whole iMac apart to reach its bay. I'll also have to obtain a mounting kit to fit the 2.5" SSD for the 3.5" harddrive.


I'll also have to reinstall macOS, either on the new SSD or to replace the locked version on the old harddrive. An iMac G3 can run macOS 10.4 Tiger, but there is a catch: 10.4 requires a firmware update, which is neither present on my iMac nor can I install it because the installed macOS is locked. To avoid any problems I'be procured a retail version of macOS 10.3 Panther, which should run fine.

I'll keep you updated as soon as I make progress!

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