Recently, the OEM ATI 9800 Pro in my G5 started showing multiple screen artifacts. These things were not small or sparse. Instead, they covered about 50% of the screen, getting in the way of everything. The artifacts were bright yellow and highly annoying, therefore they could not stay. After going through the normal troubleshooting techniques, it was determined that the GPU on the video card was overheating. Multiple actions were required to conquer the heat, and they are laid out in the following article.


This is a screenshot of what the artifacts looked like on my computer. Click on the image for a full screen version.

The first thing that was tried was cleaning the heatsink on the video card. This has been multiple times in the past. The design of the heatsink seems to attract all dust that floats into the case; so it really gets caked with dust, and therefore the airflow is restricted through the slots. Unfortunately, the dust removal didn't help, so the heatsink was pulled off the card, to allow for cleaning of the dust lodged under it. That's when the thermal cement that ATI used to attach the heatsink to the GPU became the main culprit. This stuff was a gross yellow color (similar to how newspapers yellow with age), and only half covered the GPU.

Obviously, the heat generated by the GPU was not getting properly transferred to the heatsink. So, some Arctic Silver® Céramique™ thermal paste was purchased to replace the old gunk. The Céramique™ variety of thermal paste is unique in that it is completely non-conductive, so it can get in places it shouldn't, and it won't do any harm to the system. Plus, it has been shown to drop temperatures between 3-10F below what many other thermal pastes perform at. For this particular situation, it was estimated that the temperature drop should be nearer to the 10F side. Because of the quality, and quantity of the existing thermal cement, it could be even higher.

But before putting the new thermal paste on the GPU, The GPU and heatsink have to be as clean as possible. Any dust, dirt, oil, or remaining thermal material will reduce the effectiveness of the new thermal paste. The best way to clean the old compound off the GPU (and heatsink) is to use some acetone (available at any hardware store), and a little elbow grease. It took about half an hour of rubbing with acetone soaked Q-tips to get the GPU completely clean. The persistence paid off, and resulted in the shiny surface shown in picture two.

Next, a small layer of thermal paste needs to be applied to the GPU. A dollop about the size of a pea is more than enough. Then, use a business card or similar object to spread out the thermal paste, so that it becomes evenly distributed (picture three). Then, replace the fan, and back in the G5 it goes.

The first startup with the new thermal paste was not as smooth as expected. The G5 hard froze after about five minutes, and required a hold-the-power-button shut down. The G5 was re-opened and the video card heatsink tested. It was extremely hot to the touch. A combination of two things is suspected to help build up a massive amount of heat. For one, the temporary Radeon 7000 was still in a PCI slot, trapping the hot air coming off the closer to the card. Furthermore, according to the instructions for the thermal paste, it must be in use for about 24 hours before it really gets set (fills in all the microscopic cracks).

FAQs about the overheating

1. Was the card ever subject to overclocking?
No.
2. Did this problem occur right away
No, it didn't start until almost 2 years of use.
3. When the artifacts started, did they ever go away?
Yes, sometimes putting the computer to sleep for a few minutes temporarily got rid of them.
4. Are you sure this was not a driver issue?
Yes, the same problem came up with multiple different Mac OS X versions.

A 9 inch circular fan was placed in front of the G5, to force more air through the G5, while the G5 was started up again. This time, the G5 ran for about 4 straight hours with no artifacts and no freezing. Regardless of this run, the problem could not really be declared as fixed just yet.

What about when the air temperature gets too warm, and the PCI slot fan can't keep up again? Well, this is why an extra 80 mm case fan was to be added. The first thing that must be done is provide power for the fan. The only available molex connector in G5 computers is connected to the optical (Combo or Super) drive. Therefore, a Y power splitter must be installed. This is actually quite simple. Open the two levers holding in the optical drive, remove the cables connected to the drive, and then remove the drive itself. Attach the input end of the Y power splitter to the power connector that was just in the optical drive, and one of the outputs of the splitter to the drive. The other end of the splitter is routed down trough the opening that the IDE cable goes through (see picture five), and the drive is reinstalled. The whole process will only take 3-5 minutes.

As for the type of fan, an inexpensive, quiet 80mm case fan will do. However, the G5 has no place to mount extra fans, so this is where positioning the fan correctly becomes an issue. Seeing as the G5 has such tidy looking innards, the fan placement must look good while pushing air over the video card. This becomes increasingly difficult it is realized that the plastic air deflector, which must be installed for proper service, cuts off many of the good angles for blowing towards the video card.

However, a standard the 80mm fan is 25 mm think, which means it fits perfectly between the PCI slot fan, and the extra-length PCI card holders. This is not where the fan was originally envisioned to go, but after testing it there, it seems like this location will work fine. Since the new fan has a higher RPM and CFM (cubic feet per minute) air flow than the standard PCI slot fan, the new one kind of takes over. With the fans set up this way, there is quite a bit of air movement over the video card, and much more air coming out of the back than ever before.

Since installing the new fan and putting the new thermal paste on the GPU, there have not been any more screen artifacts or video card related freezing (even when playing games such as UT 2004). The total cost for this project was about $25 (thermal paste, fan, y-adapter, and shipping costs). This is about 1/10th of what a new video card would have cost. Also, because the noise rating of fan purchased is about 24dB, the overall noise coming from the G5 did not change significantly, especially with that loud Radeon 9800 fan in there. Consequently, the end result is definitely a positive one.



Here is the ATI 9800 with the fan/heatsink combo attached.

After a lot of cleaning, the GPU is now very shiny (with a bit of left over yellow thermal cement around the edges).

A thin layer of Arctic Silver® Céramique™ thermal paste was been applied to the GPU.

The Arctic Silver® Céramique™, and the box it came in. What a waste of packaging material.

The end of the Y power splitter which provides power to the fan.

The fan installed into the G5. There are no mounting brackets for extra fans, so it was placed between the PCI slot fan and the PCI card holders.
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