Keeping your iMac 27" cool

My I7 iMac 27" computer had some issues a couple weeks ago; my local Apple Store, while very helpful, was unable to repair it within their usual window.  So they offered me a replacement.  That was unexpected and appreciated!  Thing is, the new 2011 models are faster so my 2010 I7 was going to be replaced with a 2011 I5.  True the performance numbers of that I5 are better than my 2010 I7, but I wanted the I7; I do a lot of processor-intensive and memory-intensive work on this box.  Easy, I could pay the difference between the I5 and I7.  I think my credit card was out before I uttered 'yes'.  This is a pretty good way to handle a repair that went too long.  Likely the ultimate problem with repairing my old 2010 model was availability of a replacement part.

The replacement only had a 1T drive while my old unit had a 2T upgrade.  They gave me my old drive with the idea of putting it in an external enclosure -wink-.  I swapped the internal 1T for the 2T and was up and running just fine.  For the record, that doesn't go fine if the difference in hardware is significant between the boxes (in the Mac or Windows world).  For me, it involved getting a Thunderbolt driver upgrade.  I didn't care as I was still on Snow Leopard and was waiting to upgrade to Lion until my project was over.  So much for procrastination!

Because I swapped the hard drive, I downloaded a couple diagnostic applications to make sure things were working correctly internally.  Let me assure you there isn't much room for fingers, hands, tools, or even that hard disk in a stylish iMac shell!  Because I was watching the temperature of things and fan speeds, I started checking around.

There's a fantastic free tool called smcFanControl that lets you change the minimum speed of the fans.  Normally OSX throttles the speed according to the temperature of the device it cools.  There are 3 fans: CPU, hard disk, and one for the optical drive.  The normal hysteresis OSX uses works fine, but you can keep a few things cooler with no ambient noise impact.

For me, when I edit video, the GPU (graphics processor) gets hot.  That's pretty normal for those things.  There isn't a fan for the GPU, but the optical drive's fan is positioned in the chasis in such a way that the air flows over the GPU.  Normally the optical drive's fan runs at a minimum 1,000 rpm speed, but I bumped mine up to 1,400 rpm minimum and the GPU routinely runs 10-12ºC cooler.  Cooler is always better!  I couldn't hear the difference between 1,000 and 1,400 rpm so no worries about a prop-plane landing on your desk.

A note about smcFanControl. You can choose which fan's speed you want displayed in the menu bar.  You'd assume the temperature shown is of that fan's target (CPU, HD, or optical), but it is always the CPU.  Just an FYI.

Another indispensable widget for monitoring things is iStat Pro.  A well done widget.