Installing Powerlogix 1.5GHz 7447A CPU Upgrade for Power Mac G4 Cube
First up, I had intended to purchase a chip with a VRM bypass but when it arrived, I found that I’d mis-ordered and got a vanilla version without.
I checked the website more closely and yes, indeed the version I had ordered did not have the VRM.
I would have sent it back, but unfortunately, I ordered it from OWC in the US, so that’s not going to happen.
Here are some extra hints if you want to replace your CPU with a Powerlogix one. These are not complete instructions in and of themselves.
Before you start, watch the video and print and read through the instructions. They are clear on most counts but I found a few areas lacking.
Here I’ll list a few of the difficulties I faced while also listing the outline of the instructions
(in a nutshell)
- Insert the CD with the Cube powered up. Then shutdown the Cube
- Now hold down the programmers button and keep it held until the power light flashes rapidly then press and hold C until the firmware screen appears.
- At the menu
- Press 4
- Wait for the process to complete.
- Press 5 if you use OS 9.
Now this bit was a bit worrying, nothing was mentioned what to do after the above steps.
- Just press the option to shut down the Cube
- Proceed with the disassembly.
Graphics Card and VRM
- Ground yourself.
- Remove all cabling.
- Pop the chasis.
- Remove the top plate.
- Be careful with the power connector between the top and the chassis. It’s quite short.
You do NOT need to disassemble the whole chassis in order to remove the CPU.
- Just turn the cube on its side (GFX card up) and remove the two posts. Remember which way they go, they look very similar but won’t fit if you get them in the wrong place or the wrong way around!
- On this side of the motherboard, you only need to remove three screws.
Removing the Video Card
The first real challenge you will encounter is removing the video card. The cube is tight and the card is connected to a riser from the motherboard rather than directly to the motherboard itself.
- MAKE SURE YOU’VE REMOVED THE TWO SCREWS that hold the GFX card to the frame. They are located on the base of the Cube and flank the VGA and ADC connectors.
- Remove the Video Card and Riser card together. It’s not possible to remove the card by itself.
The main difficulty is that the ports are stuck through holes in the base, which prevents you from lifting the GFX card and riser vertically, you have to lift just the point shown below.
Don’t worry, the connector is quite tough and the angle won’t break any pins or edge connectors if you are careful.
Try not to lift the GFX card out too far at first and be careful of the wires connecting the GFX card to the motherboard.
If you are having difficulties with the GFX card assembly, you might want to remove the VRM first, which is considerably easier to get out.
The black connector shown below comes off easily. Just push down on the protruding part of the clip like a clothes peg and pull the clip out.
Try as I might, I was unable to remove the brown connector shown in the picture above.
Instead, I just pulled the GFX card from the riser and hung the riser over the side of the chassis, out of the way, making sure the light grey wire (shown towards the right of the above photo) was OK.
Removing the VRM
Once the GFX card is out of the way, it’s relatively easy to remove the VRM module (That’s the other riser on the right), opposite the RAM slots.
Since I had some difficulties removing the GFX card, I removed the VRM first, to give me more space, but the principle is the same.
There is a little grey catch toward the back of the unit, next to the VRM module.
- Use a screwdriver to release it by sliding the catch to the left (if oriented as shown below). Note that there is very little feedback from the clip. Just push it back gently while pulling the VRM up and out, vertically.
Extracting the motherboard
In order to extract the motherboard, you need to ensure you have done all of the following:
- Removed the GFX card.
- Removed the VRM.
- Unscrewed the two motherboard screws along the front edge of the board as shown in fig 3.
- Removed the “unique screw” from near the VRM. (fig 7)
- Removed the “long screw” from near the memory slots. (fig 7)
- Unscrew the three, spring-loaded screws from around the large grey chip in the middle of the motherboard and pull them out vertically. Mine were quite stiff and required wiggling to get them out.
Before you can extract the motherboard, it has to be released from the big central heatsink beneath it, which due to heat and time will have fused itself to the CPU’s heatspreader because of the thermal sheet between them.
I found the method used to separate the two from each other very difficult. Perhaps because my screwdriver was too big. I couldn’t get it between them to start prying them apart.
- I started from the corner by inserting my screwdriver and twisting gently. The heatsink came away easily enough.
Once you’ve lifted the motherboard away slightly from the big heatsink, pull it towards you, away from the bottom of the case, with all the ports on it and parallel to the central heatsink.
Remember, there are two posts guiding the rear of the motherboard. If you lift the motherboard rather than pull it towards you, you risk the motherboard’s supporting corners being snapped.
Note that the ports on the bottom of the Cube are pushed through holes in the base. These holes are sealed with a kind of metallic springy foam, probably for shielding.
You will have to pull the motherboard away from the base with a little bit of force, since the springy foam may have got quite hard with time.
Replacing the CPU and heatsink
- Remove the old CPU carefully.
- Replace with new CPU.
This next part is optional, but I hightly recommend it
- Scrape off the old thermal compound from the back of the big black central heatsink.
- Apply a thinly spread layer of heatsink compound to the new CPU’s heatspreader.
Install the base fan – DO NOT FORGET. THIS IS NOT OPTIONAL. Running the upgraded Cube without a fan will destroy it!
Now follow the instructions and put everything back together.
Once you hear the Apple Bong, CHECK THAT THE BASE FAN IS ROTATING AND BLOWING AIR UPWARDS. IF THE FAN FAILS, SO WILL YOUR CUBE.