First Look: From the Lab: 2.8GHz iMac benchmarks

Apple’s recent round of iMac updates narrowed the all-in-one desktop line to three configurations—two 20-inch models offering 2GHz and 2.4GHz Core 2 Duo chips, respectively, and a 24-inch desktop with a 2.4GHz Core 2 Duo processor. Those are the three models Apple lists on its iMac tech specs page, and those are the three models we reviewed.

But those aren’t the only three configurations available. Apple offers a host of build-to-order options at its online store, where you can tweak the amount of RAM, the hard-drive capacity, and (if you opt for the 24-inch model) even the processor clock speed to your liking. Apple also offers a custom configuration—a 24-inch iMac powered by a 2.8GHz Core 2 Extreme processor. This model features a 500GB hard drive and 2GB of RAM to go with the 8x SuperDrive and ATI Radeon HD 2600 Pro graphics that also come with the standard 24-inch offering. The price for this extra clock speed, memory, and storage: $2,299 , or $500 more than the 24-inch 2.4GHz iMac Core 2 Duo .

While it’s not our policy to mouse-rate build-to-order configurations, we’re still as interested as you are to find out what that extra $500 buys you in terms of performance. So we put the 2.8GHz iMac through our battery of tests and found it tallied a 10-percent improvement over the Speedmark score of the 2.4GHz model.

Though Intel’s Core 2 Extreme lineup includes the company’s first four-core chips for desktops, the build-to-order iMac uses the mobile version of the Core 2 Extreme. And that mobile version is pretty much identical to the Core 2 Duo chips found in the standard iMacs—the main difference is the faster clock speed.

That faster chip proved especially helpful in processor-intensive tests, like the ones involving Cinema 4D and Compressor 3. In those two tests, the 2.8GHz iMac was 15-percent and 14-percent faster than the high-end 2.4GHz model, respectively. The 2.8GHz iMac scored faster results in our tests as well, though not by as big a margin.

2.8GHZ Aluminum iMac Benchmarks

Speedmark 4.5 Adobe Photoshop CS3 Cinema 4D XL 9.5.21 Compressor 3 iMovie '08 iTunes 7.3.2 Unreal Tournament 2004 Finder
OVERALL SCORE SUITE RENDER MPEG2 Encode Export Movie MP3 ENCODE FRAME RATE ZIP ARCHIVE
24-inch iMac Core 2 Extreme/2.8GHz 304 0:51 0:46 1:45 3:35 0:46 86.0 1:49
24-inch Aluminum iMac Core 2 Duo/2.4Ghz 277 0:56 0:54 2:02 4:04 0:54 87.7 2:02
20-inch Aluminum iMac Core 2 Duo/2GHz 253 1:04 1:05 2:18 4:41 1:04 70.1 2:29
24-inch iMac Core 2 Duo/2.33GHz 266 1:05 0:57 2:03 4:35 0:56 86.7 2:13
>Better <Better <Better <Better <Better <Better >Better <Better

Best results in bold. Reference system in italics .

Speedmark 4.5 scores are relative to those of a 1.25GHz Mac mini, which is assigned a score of 100. Adobe Photoshop, Cinema 4D XL, iMovie, iTunes, and Finder scores are in minutes:seconds. All systems were running Mac OS X 10.4.10 with 2GB of RAM, with processor performance set to Highest in the Energy Saver preference pane when applicable. The Photoshop Suite test is a set of 14 scripted tasks using a 50MB file. Photoshop’s memory was set to 70 percent and History was set to Minimum. We recorded how long it took to render a scene in Cinema 4D XL. We used Compressor to encode a 6minute:26second DV file using the DVD: Fastest Encode 120 minutes - 4:3 setting. In iMovie, we exported a 6minute:41second movie as a 480-by-272 resolution, H.264 file for mobile devices. We converted 45 minutes of AAC audio files to MP3 using iTunes’ High Quality setting. We used Unreal Tournament 2004’s Antalus Botmatch average-frames-per-second score; we tested at a resolution of 1,024 by 768 pixels at the Maximum setting with both audio and graphics enabled. We created a Zip archive in the Finder from a 1GB folder. To compare Speedmark 4.5 scores for various Mac systems, visit our Apple Hardware Guide .—MACWORLD LAB TESTING BY JAMES GALBRAITH, JERRY, JUNG, AND BRIAN CHEN

Not surprisingly, the only test to not show any improvement involved our Unreal Tournament frames-per-second test. 3-D games such as Unreal Tournament rely much more on their graphics processor than on their CPU—as mentioned above, both the 2.4GHz and 2.8GHz systems use the same ATI graphics processor with 256MB of GDDR3 memory. As a result, both turned relatively similar scores, with the 2.4GHz model squeezing out just a tad more frames per second than its 2.8GHz counterpart.

The previous generation of iMacs introduced in September 2006 also included a build-to-order CPU upgrade—from a 2.16GHz Core 2 Duo chip to a 2.33GHz processor. To see the performance difference between these two custom models, we retested the 2.33GHz with 2GBs of RAM and OS X 10.4.10. The new 2.8GHz model was 14-percent faster than the older 2.33GHz model in Speedmark, with the biggest gains coming in the Cinema 4D and Compressor 3 tests. Again, there was not much difference in our Unreal Tournament test.

[ James Galbraith is Macworld Lab director. ]

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