Thursday, August 18, 2011

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 10-12ÂșC 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.


  • Ben Strano said...

    I'v been hooked on MenuMeters for years now. When I'm mixing I always like to be able to see how hard my processors are working.

    I even have it on our laptop which does nothing but internet and email... I just like knowing.

    Although... with the macpro even my most intense mix never makes the computer think twice.

  • HalfInchShy said...

    You know, if your CPU isn't working hard with your intense mixes, it's because you aren't using enough cowbell...

  • James said...

    Love Apple's customer service. I had an issue with my wife's Imac 2 weeks after I bought it. They gave me a brand new computer and let me keep the old keyboard and mouse.


  • Qwas said...

    Thanks for the input on smcFanControl. My 24" iMac has always been very hot to touch on the back. I've been wanting a fan control program but never found one. With smcFanControl I turned the fans up to about 2/3 full value. The computer started cooling off in minutes.

    Like Ben, I've been using MenuMeters. It's great for monitoring CPU activity and I like to monitor network activity also.

  • HalfInchShy said...

    What I like most about smcFanControl is that it only affects the minimum speed; if you could set the maximum too low then run your machine hard, you could do thermal damage. This app doesn't let you do that.

    That said, though, there is a hardly documented way to run the tool from the terminal to set the maximum speed until next reboot. I have to use it because of an incompatibility with the HD thermal sensor in this new iMac and my previous drive: basically it always thinks it is too hot and runs the fan at over 5,000 rpm! If it had wings...

    Anyway, glad it worked for you!

  • The Warrior Workshop said...

    I thought Mac's were problem free?