Upgrading G4 CPU

Upgrading the CPU on my G4 turned out to be a lot more involved than I originally thought so here’s the process in case anyone else (or myself) needs it in the future. This is the exact process I used to upgrade the CPU in my Digital Audio G4. Should be the same for any logic board with an AGP slot.

I think this applies to any aftermarket CPU upgrade 1.5GHz and above (which should be the MPC7447/MPC7447A cpus). 1.4GHz and below shouldn’t need more than just the latest Apple firmware.

You must update the firmware and extensions using your existing CPU before installing the new CPU or it will not work.

This guide and the links in this guide will work in IE5 and IE5.1 on OS 9.2 if your mac happens to be connected to the internet. Simply visit the regular http version of this site:

http://moyashi.party/dev/powerpc/8

Start with a fresh install of OS 9.2

I used 9.2.1 on my machine since it’s the disc I had handy, but these instructions should be the same for 9.2.2.

Install 9.2 as usual.

Update to latest Apple firmware

Now you’ll want to update to the latest official Apple firmware.

Download it here.

  • Run the official Apple firmware updater
  • When it’s ready press “Close” and your computer will shut down.
  • Hold the programmer’s button down while you power on again, continue holding the programmer’s button until you hear the long tone.
  • Once you hear the tone, release the programmer’s button.
  • A bar will appear along the bottom of the screen indicating firmware update progress if it all worked.

Update to Sonnet’s patched firmware

Same process as with the official Apple firmware.

Download the patched firmware here. Follow the same process as before:

  • Run patched firmware updater, computer shuts down.
  • Hold programmer’s button while you power on, keep it held until you hear the tone.
  • Wait for firmware update to complete.
  • A message should appear when it finally boots to indicate that the patched firmware is now installed.

Install the patched multiprocessing CPU extension

Download the extension here

Place it in TODO

At this point I would highly recommend imaging the drive and keeping a backup somewhere safe in case you ever need to “reinstall” MacOS 9.

This is optional but there can be issues using the installer CD with the newer CPUs, so it’s much easier if you can just re-image the working version with the patched extensions and so on.

Personally I just take the SATA drive, put it in an external SATA dock on my main PC, and use the Disk Utility that comes with Ubuntu MATE to image the drive. Use your own preferred tool here.

Finally, install the new CPU

At this point everything is in place that after installing the new CPU it should just boot first time without any random freezing.

Personally I did encounter some problems where I believe the PMU may have crashed and even hitting the PMU reset button on the board did not help. What did fix it was unplugging power from the board, removing the battery and leaving it for around 20 minutes.

After that I just re-installed the battery, waited about 30 seconds for the PMU to start, plugged power in, then it booted and has been working just fine ever since.

SOME DETAILS TO BE COMPLETED