Gauging Snow Leopard’s speed boosts

Apple describes Snow Leopard as a top-to-bottom refinement of existing features. One major goal of those refinements: Improved performance.

Snow Leopard aims to run leaner and faster on current and recent Macs, in part by dropping support for legacy Power PC systems and focusing solely on Intel-powered Macs. And while some of Snow Leopard’s potential performance gains won’t show up until software developers optimize their applications for the new OS, others are apparent right now.

To check the performance benefits, we tested Snow Leopard on three different systems: a 20-inch iMac Core 2 Duo/2.66GHz ( ) with 2GB of RAM; a 3GHz Xeon 5300 eight-core Mac Pro with 4GB of RAM (this Mac Pro was released in April 2007); and a 15-inch MacBook Pro Core 2 Duo/2.8GHz ( ) with 4GB of RAM. The hard drives in each system were partitioned into two equal sizes, and we installed Leopard (OS 10.5.8) on one partition and Snow Leopard (OS 10.6) on the other. We booted into one OS, timed different tasks, then rebooted into the other OS and clocked those same tasks.

What’s faster

The good news is that, of the 16 tests we ran, eight were indeed faster under Snow Leopard compared to Leopard. For example, an initial Time Machine backup to an external FireWire 800 hard drive was between 10 and 15 minutes faster in Snow Leopard. Snow Leopard was, on average, 32 percent faster with Time Machine backups across the three systems. Of course some of that performance benefit is due to Snow Leopard’s smaller hard drive footprint – the iMac, for instance was backing up approximately 27GB worth of files under Snow Leopard, while Leopard’s files and folders took up around 34GB of disk space.

Snow Leopard was also faster than Leopard during shutdown. On our iMac and Mac Pro, it took 7 seconds to shut down when running Leopard, but only 4 seconds when running Snow Leopard. For people using a desktop Mac, that difference may seem trivial. But laptop users who find themselves tapping their toes waiting for shut-down should take notice: Snow Leopard took half as much time as Leopard to turn off our MacBook Pro, 3 seconds versus 6 seconds.

Our Compressor test, which involves encoding a .mov file using Apple’s H.264 for Video Podcasting presets, was 2 percent faster on our iMac and MacBook Pro and 4.5 percent faster on our Mac Pro when running Snow Leopard than when running Leopard. Zipping a 2GB folder in the Finder was 6.5 percent faster on the iMac, 8 percent faster on the MacBook Pro and 11 percent faster on the Mac Pro. Importing 150 photos from the hard drive into iPhoto, the iMac was nearly 8 percent faster under Snow Leopard, the MacBook Pro improved 11 percent, and the Mac Pro knocked a full 21 percent off the time it took compared to Leopard.

Snow Leopard also shaved a few seconds off the time to scroll through a large PDF document in Preview and opening a large Word document in Pages. Safari’s JavaScript performance in Snow Leopard increased by an average of 33 percent, according to Webkit.org’s Sunspider benchmark results.

What’s not faster

Of the other eight tests that we ran, two showed virtually no performance difference between the two operating systems, and two tests actually ran faster under Leopard.

We saw very little change in the time it took to start up our Mac Pro and MacBook Pro using either OS when connected to our local wired network. The iMac was a little faster starting up in Snow Leopard, but only by a couple of seconds. Similarly, our Photoshop test suite times were unchanged on our iMac and Mac Pro, while the MacBook Pro finished just 2 seconds faster when running Snow Leopard.

The two tests that ran consistently faster under Leopard were our Finder duplication of a 1GB file, which took 2 to 3 seconds longer when running Snow Leopard, and a wake from sleep and connect to the network test that took 1 to 3 seconds longer to finish on Snow Leopard.

Mixed results

In the four remaining tests, we saw mixed results: On any given test, Snow Leopard was sometimes faster, sometimes slower, depending on the machine.

Unzipping a compressed file in the Finder and importing a camera archive into iMovie both were slower under Snow Leopard on the iMac, but Snow Leopard was faster than Leopard on the MacBook Pro and Mac Pro. Exporting a project from iMovie using that application’s iTunes: Mobile preset, Snow Leopard was faster on our iMac, slower on the MacBook Pro, and exactly the same on the Mac Pro. Converting two CDs worth of AAC-encoded song files to 256Kbps MP3s in iTunes took considerably less time using Snow Leopard on the iMac and MacBook Pro, but longer when running Snow Leopard on the Mac Pro.

Here’s a chart showing the percentage speed boosts (above 100%) or speed reductions (below 100%) we found when upgrading a system from Leopard to Snow Leopard. A score of 100% indicates that the test took the same time on both systems.

More to come

These preliminary results are encouraging. Half of our tests showed improvement right out of the gate and only a couple showed any backwards progress. Apple will, no doubt, continue to refine and improve performance of the OS in the weeks and months to come. And applications, including Apple’s own, will be optimized to take advantage of Snow Leopard’s processor technologies like Grand Central Dispatch and Open CL.

As these technologies evolve, so will our tests. We are already hard at work developing our new Speedmark 6 benchmark. We’d love to get your input on which applications and tests you’d like to see included in the next version of our overall system performance benchmark. Feel free to post your suggestions in this article’s comments section .

[James Galbraith is Macworld’s lab director.]