Mac Pro overheats just at the wrong time…

August. Always the hottest and busiest month of the year. For us, all the boat shows are approaching, so many of our marine clients come up trumps with lots of lovely design work for us.

Just the moment when you don’t want your primary workhorse computer to start displaying death throes.

I wrote this post as a reply to a similarly distressed designer on the Apple forums, but I though that others might have had the same experience – so I’ve put it here as well in the hope it might help. My machine is behaving itself now, by the way…

Original query:

Unexplained (Mac Pro) Powering Down

Symptoms: I have been experiencing random shutdowns / power-downs where the machine will simply turn off instantly and then restart 10 seconds later. this has happened about 15 times over the last month.

I had this exact problem which I managed to resolve the problem using two software utilities.

I’d be working away and (usually around mid-afternoon) my Mac Pro would unexpectedly just turn itself off as if there was a power-cut. Then it would restart itself and be OK for a while.

My first thought was that it might be related to the graphics card; it has eaten one before and the problem seemed to be worse when more than one monitor was attached. I called a local computer guy who has helped me with the Mac Pro before – and he suggested that it might be the power supply at fault. The problem here is that you could start throwing money at replacing parts, whilst not really knowing whether or not it’s going to fix the issue.

The other thing it was suggested that it might be was that it was overheating. This seemed to be a reasonable theory, as the studio is warm and the power-downs seem to occur late in the day.

So the first thing I did was a search on Google for Mac Pro temperatures. The first utility I found was Hardware Monitor (shareware).

This shows the current temperature of every component that has a sensor in the computer. The hottest thing in my list was the Northbridge Heat Sink which was getting up to 88°C (190°F). A small amount of research made it clear that this was a bad thing… if the heat sink was this hot, how hot must the chip have been? The Northbridge Chip ships with a thermal paste applied. Over time, this can literally ‘bake’ off, resulting in hotter operating temperatures. If it gets too hot, the computer powers off.

This also explains why the internal fans weren’t kicking in sooner – they’re set at a lower idling RPM which eventually just isn’t enough to prevent the overheating.

Enter utilty 2 – Fan Control (freeware).

Once installed, this utility is accessed via the System Preference pane.

I downloaded and installed this (while the Northbridge Heat Sink temperature was topping 88°C again) and the fans instantly kicked in – in a big way. They brought the sink temperature down to about 45 / 50°C. I set the minimum fan RPM to 1000 and the upper and lower thresholds to between 40°C and 70°C.

By this time I was down to one small monitor, and after a couple of days of no problems, I put my 30″ cinema display and additional 19″ monitor back on – and waited. That was 10 days ago and the problem has vanished – and as far as I’m concerned, solved.

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