It seems the 2009 Mac Pro has an issue. When it idles, the processor temperature is about 35 C (95 F). When you play music in iTunes or any other application, the temperature rises to 50 C (122 F) or even much higher in a short amount of time. I read about the issue on MacRumors (article here) and and in a discussion on the same site here.

I have a late 2009 Mac Pro and I have tried to reproduce the issue. All I had to do to succeed in this was play a song in iTunes and within half a minute the temperature of the processor of my Mac Pro (a 2.66Ghz quad core) had risen by 15 degrees Celcius. That’s 27 degrees Fahrenheit. Rather silly when you think playing audio is a simple task for a fast processor like this Nehalem.

In discussions I’ve read the issue doesn’t exist when running Windows on the Mac Pro. This makes me think it’s a software issue. Well, at least software glitches can be easily fixed. Let’s hope Apple takes this issue seriously. So far they haven’t acknowledged it.