As most of us know, Apple did a great job with air circulation in the PowerMac G5s. There are four thermal zones, each one independently controlled for maximum air flow with minimum noise. For the most part, they did a great job with this.All except for one part, the PCI/AGP bus section.

The four cooling zones. I am concentrating on the second one.

In that section, there is one intake fan, which blows air over the PCI and AGP cards, and exits out the back of the computer. However, the amount of perforation (little case holes) in that area is severely lacking. As shown in a picture below, only about 1/3 of the back of the computer is perforated in this area (the other two thirds taken up by the PCI covers). So, I figured, why not perforate them myself, and allow the air to flow over the installed Radeon 9800 a little better. And that's what I did.

I started by marking the places where I wanted the holes with a pencil. Then, with the holes marked, I brought the PCI covers to a drill press I had access to. Here is where the trouble started. First, not much clamping was available, so it was hard to position the covers correctly. Furthermore, because the material used to make the covers is so soft, it was very difficult to drill a perfect hole, plus the metal itself liked to bend around. If there were some center punchers, those may have worked better (also, smaller holes may have been a good idea).

Nonetheless, I kept plugging away at it. When I was done drilling, I pounded the covers back to being straight, and filed out the holes a bit to make them more rounded (more filing could be useful). The end look isn't as clean as I hoped (better tools could have rectified this), but will still get the job done.

The newly perforated covers were installed back in their rightful spots, and the G5 was turned on. I opened up a program called OpenMark which taxes the Graphics Card for about 6-7 minutes running an OpenGL benchmark. While it was running, I could feel the hot air rushing out of those holes. Without the holes, the hot air would be forced to find another exit, warming up other parts of the computer. Overall, I see this as an improvement. It would be nice is if looked a bit better, but the increased airflow is what I was really after.

The backside of the G5 with the normal PCI slots covers.	An angled view of that same shot.	This is the fan that cools the entire PCI/AGP bay. Hopefully this will be able to spin a bit slower when the PCI bay heats up.
An inside view of the covers. As we can see, there is very little case perforation around here.	All the holes are marked for a nice line of holes (if only it would have worked out that way).

Here are the PCI covers with the holes cut. As you can see, the holes didn't follow the lines like I wanted.	Newly perforated covers installed. There is a lot more room for exit airflow now.	The back view of the G5 with the modified covers. There is still some filing that can be done.
Again, the same shot as above, only angled.