The Brad Hole

A while back, I wrote about thermal runaway problems I was having with my then-new 2.5GHz G5. To bring you, the internet, up to speed, I ran a utility that tracked CPU temperature and noted that one of them was getting rather toasty - above 200 degrees F. Once that CPU hit a certain temp (which I can't remember now), the system would force itself to sleep. I was able to work around it by setting my Energy Saver settings for the CPU to "Reduced", which eliminated the problem in the short-term.

The real trick here is that I've come to rely on this Mac to do the bulk of my day-to-day work, since pretty much any game we work on now is a bit too manly for my old 800MHz G4. Several months back, this G5 began exhibiting a new problem - it sometimes wouldn't restart. If I had to install a security update, an OS update or even if the power went off, it was a game of Russian roulette getting the G5 to power back on. Most of the time, I could let it sit for an hour or two and it'd start up cold, so I got to where I'd just avoid cycling the power at any cost. My plan was to take it in for repair when we moved, but because it had been so long since I had to reboot I had forgotten about the issue until after we'd moved and I had to turn it back on (which it did, on the first shot).

Things came to a head 2 weeks ago while I was working on Tiger Woods 2005. I was trying to track down a bug whereby the terrain wasn't rendering on the 8500 card in my G4. I forced the GL profiler in the G5 (which has a Radeon 9600 card) to use the 8500 driver, something I'd done before with mixed success. Unfortunately for me, this caused a kernel panic and I had to reboot. But this time...it was personal!

The G5 would not come back with any amount of coaxing, so I made a very reluctant call to AppleCare to set up an incident. I had a pretty strong feeling that the CPU module was to blame here, since the thermal runaway was the first issue I encountered. However, the AppleCare rep had me go through the usual basic steps first: reset the PRAM ("But this Mac - it doesn't even play the startup chime!"), try to boot into Open FIrmware ("Did I mention no startup chime?"), plug in my original Apple keyboard ("Do you think this will cause it to play the startup chime?"), and unplug my ethernet connection. After humoring the rep, she determined that it was probably a firmware problem with the power manager and determined that it was under warranty and that I should bring it in.

I took it to the local Apple Store and explained the issues. They ordered new parts and 3 days later, I had a working G5 again! Turns out that the inability to start up was a faulty Radeon 9600 card (apparently this is a known issue). It also turns out that thermal runaway was like I suspected - a faulty CPU.

The best news though : this G5 runs far more quietly now than my G4. After really pushing it hard on the highest CPU settings, I can't get the fans to rev up to anywhere near full speed like I could before, and the temperature for both CPUs hovers around 175F at full stress. The difference from before is like night and day, and now I can't wait to retire this G4 and eliminate what is now pretty much the only source of noise in my office.