Faster than ever: Macworld Lab speed tests the mid-2011 iMacs

We’ve already shared the results of our benchmark tests for the $1999 27-inch 3.1GHz Core i5 iMac, one of four new iMac configurations released by Apple this week. We’ve had the chance to finish testing the remaining three standard-configuration models, with our results showing a significant boost for the new iMacs over the models they replace. However, not much differentiates the performance of the four new iMacs among each other.

The new entry-level iMac is a 21.5-inch, $1199 model with a 2.5GHz Core i5 quad core processor, a 500GB hard drive, and AMD Radeon HD 6750M graphics with 512MB of video memory. The other 21.5-inch iMac has a 2.7GHz Core i5 quad core processor, a 1TB hard drive, and AMD Radeon HD 6770M graphics with 512MB of video memory for $1499. A 27-inch iMac with otherwise identical specifications to the $1499 iMac costs $1699. And finally, the previously benchmarked 27-inch iMac is a $1999 system with a 3.1GHz Core i5 quad core processor, a 1TB hard drive, and AMD Radeon HD 6970M graphics with 1GB of video memory. All four systems run on Sandy Bridge processors from Intel.

Macworld Lab’s overall system performance test suite, Speedmark 6.5, showed these four new Sandy Bridge iMacs to be considerably faster than the systems they replace. The new $1199 21.5-inch, 2.5GHz Core i5 quad core iMac was nearly 24 percent faster overall than last year’s entry-level 21.5-inch iMac, which had a 3.06GHz Core i3 dual core processor. As you would expect, the new iMac showed the most improvement in applications that could take advantage of four processing cores. The new entry-level system was 37 percent faster in our Handbrake encoding test, 34 percent faster in our Cinebench CPU test, and 64 percent faster in MathematicaMark.

The new $1199 iMac was even faster than last year’s high-end standard configuration model, a 27-inch 2.8GHz Core i5 quad core iMac, by nearly 10 percent. In this case, the processor-intensive tests were very close, but the file duplication, zipping and unzipping a folder and opening a Word document in Pages were all considerably faster on the new $1199 iMac.

Compared to the 27-inch 3.2GHz Core i3 dual core iMac from last year, the new $1699 iMac was 25 percent faster. The older 3.2GHz Core i3 iMac also performed better than the new 2.7GHz Core i5 iMac in its file duplication and unzip tasks, but everything else was faster—sometimes much faster—on the new 2.7GHz system. Handbrake was 40 percent faster on the new model, Cinebench CPU tests were 37 percent faster, and MathematicaMark scored 70 percent higher.

Surprisingly, when compared to each other, the new iMacs logged similar performance numbers. In fact, only 12 Speedmark points separate the entry-level $1199 21.5-inch 2.5GHz Core i5 iMac and the top-of-the-line $1999 27-inch 3.1GHz Core i5 iMac.

Looking at the new $1699 27-inch 2.7GHz Core i5 quad core iMac, we see that it outperforms the entry-level $1199 system by just 4 percent, overall. The close scores can be attributed to the 500GB hard drive in the $1199 model which was faster at file duplication and unzipping folders than the other three models with their 1TB hard drives. iMovie, iTunes, Photoshop, Handbrake, Cinebench, and Mathematica were faster on the $1699 system.

The new 27-inch 2.7GHz system—which uses the same processor, graphics and hard drive as the 21.5-inch 2.7GHz iMac—performed nearly identically to that model.

We initially completed all of our tests before Apple released the Mac OS X 10.6.7 Update for iMac and the iMac EFI Update 1.6. We retested with the updates installed, and found no difference in performance with our tests.

Keep in mind we’ve only tested the standard configurations so far. The new iMacs offer several build-to-order options including faster processors and solid-state drives (either as a replacement for or complement to the main drive). That latter option, in particular, could lead to some performance swings; we plan on testing the build-to-order iMacs as soon as we finish reviewing the base models.

Check back soon for Macworld’s full review of the new line of iMacs, including more graphics tests.

[James Galbraith is Macworld’s lab director.]