Alcaic Research and technology, not iambic verse.


Death of a friend – and resurrection.


About a year back, after a system update, our 2006 iMac (ATI Radeon X1600 GPU) started acting flaky. Strange visual artifacts popped up sometimes, and the machine hanged (hung?) unexpectedly. This post shows what you can do to solve this problem - partially - and I am putting it up because it took me several days to hunt through old message board posts to find it.


The root cause of the problem appears to be (shame on you, Apple) some quality problems on a certain batch of GPUs from ATI and their mounting. With the ever increasing reliance of OS X on the GPU (Quartz Extreme etc...), the component starts to heat up and some of the electrical contacts fail. That is was temperature related was very apparent last summer.


Browsing the web (I am not going to give you a long list of links, since most of this info was buried deep), the solutions fell into 6 categories

  1. Get Apple to replace the GPU subassembly. In my case: too late (even with extended warranty).
  2. Open up your iMac and clean it out, improving the airflow and (hopefully) reducing the temperature. Well, this was needed, and helped for about 3 days. Probably, opening it and cleaning it out just changed some mechanical strain that relaxed later on and the problem resurfaced.
  3. Reflow the soldering by using a hairdryer. Did not try this - the evidence seemed inconclusive and since I did not have a backup machine (I do have a backup of the data) to serve up the files in the house, I did not want to risk frying the GPU completely.
  4. Applying extra thermal paste. Didn't try this either.
  5. Using smcFan Control or Fan Control to increase the airflow. This is the one that convinced me this is the root cause, because it helped. Most of the time. But the iMac did sound like a vacuum cleaner. Most of the time.
  6. Removing the drivers. You read that right. By removing the GPU drivers, the iMac falls back on using the CPU and basic gfx, and hence the GPU is not used and does not run hot/does not corrupt anything. There is of course a trade-off: some programs that use this to payback video, and games as well, no longer work well/at all.

The last option worked very reliably. And since I only use the machine as a server, it is also the cheapest.

What do I do ?

Assuming you want to try #6, here are the steps:

  1. Reboot in safe mode (hold the shift-key immediately after the startup chime)
  2. Go to /System/Library/Extensions/
  3. Move/delete files that start with atiradeonx1000 and atiradeonx2000
  4. Reboot.


I now have a stable machine again, but I am not happy with Apple. This appears to have been a widespread problem a while back, and a divergence of the quality level I have come to expect from Apple. That it is a 6 year old machine is not an excuse - it still runs the latest OS X smoothly (which always surprises me) - I expect the hardware to live until no longer supported by the latest OS.