How-To: Upgrade the processor on an older macintosh G4

We began this story by buying an older graphite 400Mhz G4 tower from ebay.de some months ago. The motherboard and the manufacturing of the AGP G4 series, codenamed "Sawtooth", are in our opinion quite good (i.e. there weren't huge amounts of AGP G4's that failed in weird ways over time). After doing some preliminary reading we found that doing a processor upgrade for a G4 can sometimes require messy heat sink paste. Some other mac proc upgrades use the same heat sink provided with your original proc. We decided on a choice that does not require thermal paste and has a larger new heat sink and fan included: the PowerLogix PowerForce47 G4/2.0GHz with 512K 1:1 L2 Cache Per Processor. (note: we were not remunerated by Powerlogix nor did we receive free merchandise for this how-to nor is this article a review of comparable mac proc upgrades). After some trials and tribulations with the processor upgrade, we simply wanted to put this information out there to help who it may, after all we never enjoy seeing macs in the trash.

To start with, we did read the documentation shipped with our Powerlogix upgrade. This being fairly basic in some ways, we were reassured and jumped right in. To save yourself the same hurdles we met, read on.

The documentation's summary of a powerlogix in an agp upgrade:
1. Upgrade the apple firmware of the motherboard (the boot rom) to 4.2.8 or higher.
2. Upgrade the firmware again with Powerlogix's proprietary software.
3. Remove the old processor.
4. Install the new processor.
5. Boot.

Now the actual summary of our difficulties not being the point of this article, we will keep the updated summary short. To be certain, the list above is correct, but rather vague.

Summary of a powerlogix in an agp g4 upgrade should be:
0.7 Make sure you have OS 9 installed on a partition or a harddrive.
0.8 Make sure the harddrive is bootable (harddrive is master not slave) and at least os 9.1.
0.9 Download the apple boot rom updater for boot rom 4.2.8 and copy it to the desktop of os 9.
1. Launch the boot rom updater and reboot in programmer's mode.
2. Upgrade the firmware again with Powerlogix's proprietary software.
3. Remove the old processor.
4. Install the new processor.
5. Boot.

What follows is our step by step instructions. You may also want to refer to Powerlogix's documentation.

Before starting, in OS X, install the CPU Director software from the Powerlogix CD included with your processor.

You must have OS 9 installed and bootable on the machine, even if you only want to run OS X on the computer later. This is because Apple never released a firmware upgrader for the AGP G4 and many other models of the G4 line for OS X. If you only have one harddrive in your computer and that harddrive only has one partition and that partition has OS X installed, you are out of luck. OS X's Disk Utility can not repartition a disk that contains the startup volume. For us, this required that we install OS 9 on a second hard drive. Our computer did not want to install or boot OS 9 if there were any other harddrives in the machine. Also, the single harddrive with OS 9 should be set to master (pictured is our 160 gig hitachi deskstar, check the pin diagram for your harddrive):

Now if you had trouble installing from an official OS 9.2 installer cd as we did, try installing OS 9.0 and upgrading to 9.1. Realize that you must have at least 9.1 installed for the firmware upgrade. When you install your first OS (be that OS 9.0, 9.1 or 9.2), be sure to download the firmware upgrader from Apple's site and copy the Power Mac G4 Firmware Updater and the Power Mac G4 Firmware to the Desktop:

You may now upgrade the OS if you are in OS 9.0. We had trouble with the 9.1 upgrade as well and had to boot without extensions by holding down the shift key when booting. Now because you've already downloaded and copied the firmware patches to your desktop, you don't need to worry about missing extensions for the net or any other way to get those files to your computer. Double click on the Power Mac G4 Firmware Updater. It will now walk you through the installation and will finally ask you to reboot the computer in programmer mode. When the computer is off push in the programmer key and press the power button. The programmer's button has a -v- symbol inside a circle and is the concave button on the right under the power button on our G4 AGP. Release both buttons immediately after the long programmer's beep has stopped.

The computer should now show the progress of your firmware upgrade. When it has completed, eject the CD-rom drive and put in the Powerlogix CD (in our case this cd is labelled "Product Manuals & Installation Videos", but it is also the firmware updater CD). Once again push in and hold the programmer's button and the power key. Immediately after the programmer's tone stops, release the programmer's button and the power key and then press and hold down the C key on the keyboard. You will hear the computer chime the boot sound now. When the green Powerlogix firmware upgrader screen comes up, choose "4: Install all patches". (note: This picture shows "Remove all patches" because we have already applied the patch, but yours will be "Install all patches.)

When the Powerlogix firmware updater has finished and the computer has shut down, unplug all cables on the G4 and open the case. The processor is under the large silver heatsink.

Pop up the heatsink clips carefully and remove the heatsink by gently pulling straight up.

Remove the screws from the processor's card (we had three screws). Set aside the screws, you will be using them in two steps. Gently remove the CPU card by carefully pulling straight up (a bit of a jiggle may be necessary, but don't force).

Place the new processor and heatsink (all connected) on the processor connector. Line up the processor connector carefully (this may require having the G4 at eye level) and gently push down until you hear a click (a bit of a jiggle/rocking motion may be necessary, once again do not force).

Screw in the two screws you set aside into the new CPU. Try to drop the screws straight down, the cavities in the heat sink are tall.

Connect the power cable of the fan to a free connector on the 12V power of your computer.

Replace the OS X harddrive on which you installed CPU Director above and boot your machine. If all went well with your install, OS X will boot. Open the About This Mac window in the Apple menu to verify that your new processor is recognized correctly:

The Powerlogix card we use includes temperature monitoring among other things. Temperature monitoring is quite important since in our case we went from a 400Mhz to 2Ghz processor. Launch the CPU Director software and choose the "Thermal" tab to see the temperature:

Without the proc upgrade we couldn't run a realtime audio synthesis engine and with the upgrade we can. Nuf' said. We hope your installation process was less painful than ours! Go enjoy your new speedy mac.