Mac Pro Audio Update Firmware Cuts Performance Lag

A firmware update usually doesn't grab much attention--particularly if it's released in the midst of Macworld Expo. And yet, last week's release of Mac Pro Audio Update 1.0 brings welcome relief to many Mac Pro users. Our tests found that the firmware update improves the performance of the desktops Apple released last March when they're running the latest version of Snow Leopard.

To recap, the audio update firmware rolled out a week ago is meant to fix a problem where processors in 2009 Mac Pros seemed to go into overdrive when doing something as seemingly simple as playing a song in iTunes or writing data to an external hard drive. We had heard some grumbling about the problem in our Macworld.com forums, where folks complained that their processor temperature spiked whenever iTunes was playing, but it was unclear whether or not this higher temperature posed any kind of real threat to processor or system health. A post on Ars Technica indicated that performance times were adversely affected when music files were being played--as much as a 20-percent hit, according to users.

To find out what kind of performance hit the Mac Pro Audio Update 1.0 was trying to address, and how well it did at correcting the problem, we conducted a couple of tests on a stock 2.66GHz Mac Pro running Mac OS X 10.6.2 with 3GB of RAM installed. Then we downloaded Mac Pro Audio Update 1.0 and ran the tests again.

Before the update, running an Aperture 2 import test took 19 percent longer to complete when iTunes was playing in the background than when Aperture ran alone. After installing the update, we saw just a one-second time difference.

Similarly, a Compressor encode test took 16 percent longer when we ran that program at the same we were running iTunes before we installed the firmware update. Afterward, the gap also narrowed to one second after the update.

For the purposes of comparison, we ran the same tests on a 27-inch iMac with a 2.66GHz Core i5 processor. (Just once this time, as there's no firmware update to install.) We recorded a one-second difference between running the applications alone and with musical accompaniment via iTunes.

We installed iStat menus on the Mac Pro to help get an idea of what was going on under the hood. (iStat menus is a set of monitoring tools for your menu bar; you can read more about it at MacOSXHints.com.) You can see from the table that the CPU temperature sensor readings averaged around 120 degrees when running Aperture and iTunes before the update. After the update, the Mac Pro's temperature was cooler--around 90 degrees. iStat's CPU power monitor reported drawing around 72W before the update, but dropped to around 30W after the firmware update was in place. Similarly, iStat's Power Supply monitor showed the desktop drawing 165W before the update and 105W after installing the update.

Mac Pro Audio Update 1.0 only works with Snow Leopard, though it's worth noting that Mac users running Mac OS X 10.5 have also complained about the problem. Hopefully, help will be on the way to these Leopard users soon.

[James Galbraith is Macworld Lab director.]

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