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Aluminum iMac Q&A - Published May 27, 2011

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How fast are the "Mid-2011" Aluminum iMac models compared to one another? How much faster are these models than the "Mid-2011" models replaced? How fast are they compared to a Mac Pro?

With even a quick scan of a comparison between the "Mid-2011" Aluminum iMac models and the "Mid-2010" models that they replaced, it is readily apparent that the newer models have a completely different architecture, dubbed "Sandy Bridge," complete with a twice as fast DMI (Direct Media Interface) as well as processors with faster clockspeeds and faster graphics, too.

In official company tests, Apple reports that the "Mid-2011" iMac models overall are "up to 1.7x faster than the previous-generation iMac" and "up to 3x faster" in graphics performance. Specifically, this is referring to the iMac "Core i5" 2.7 21.5" (Mid-2011) and the iMac "Core i3" 3.2 21.5-Inch (Mid-2010) for overall performance and the iMac "Core i5" 2.5 21.5-Inch (Mid-2011) and the iMac "Core i3" 3.06 21.5-Inch (Mid-2010) for graphics performance. Apple declines to compare these iMac models to the high-end Mac Pro line.

Some readers might be satisfied with the official answer, but for those who appreciate objectivity -- and are more interested in how these iMac models stack up against the Mac Pro -- benchmarks and a variety of independent third-party tests also can be useful.

General Performance Overview

For a solid general overview of the performance differences between the "Mid-2011" iMac models and the "Mid-2010" iMac models as well as the "Mid-2011" iMac models and the TK Mac Pro models,'s own Ultimate Mac Comparison makes it quick to compare side-by-side 32-bit and 64-bit Geekbench benchmark averages with all other G3 and later Macs for thousands of possible performance comparisons.

The Geekbench benchmark shows that the stock "Mid-2011" iMac models -- the iMac "Core i5" 2.5 21.5-Inch, "Core i5" 2.7 21.5-Inch, "Core i5" 2.7 27-Inch and "Core i5" 3.1 27-Inch -- are roughly 25%, 31%, 30%, and 13% faster than the stock models each replaced from the "Mid-2010" iMac line.

Geekbench also shows that the fastest stock "Mid-2011" iMac model -- the iMac "Core i5" 3.1 27-Inch -- is roughly 10% slower than the slowest stock "Mid-2010" Mac Pro -- the Mac Pro "Quad Core" 2.8 (2010/Nehalem). However, the fastest custom configured "Mid-2011" iMac -- the iMac "Core i7" 3.4 27-Inch (Mid-2011) -- is 30% faster than the entry-level Mac Pro and costs 12% less.

Other Performance Testing Results

Geekbench provides a convenient overview of overall performance, but other third-party testing can be useful for a well-rounded viewpoint. Benchmarks don't always tell the full story in "day-to-day" use.

In its trademark Speedbench 6.5 testing, the industry-standard MacWorld reported:

The four new Sandy Bridge iMacs are considerably faster than the systems they replace. The new [entry-level] [US]$1199 21.5-inch 2.5 GHz Core i5 quad core iMac was nearly 24 percent faster overall than last year's entry-level 21.5-inch iMac, which had a 3.06 GHz Core i3 dual core processor. . .
The new [US]$1199 iMac even beat out last year's high-end standard configuration model, a 27-inch 2.8 GHz Core i5 quad core iMac by nearly 10 percent. . .
Surprisingly, when compared to each other, the new iMacs logged similar performance numbers. In fact, only 12 Speedmark points separate the entry-level [US]$1199 21.5-inch 2.5 GHz Core i5 iMac and the top-of-the-line [US]$1999 27-inch 3.1 GHz Core i5 iMac.

Comparing the high-end iMac "Core i5" 3.1 27-Inch (Mid-2011) to the Mac Pro "Eight Core" 2.4 (Mid-2010), the Windows-centric PCMag found:

The iMac completed the Handbrake video encoder test in a quick 1:38 in Windows and 1:28 in Mac OS. This is even faster than the massive (and expensive) Apple Mac Pro, which took 2:22 in Windows and 1:55 in Mac OS on the same test. . . Likewise, the new iMac is an excellent Photoshop CS5 machine: It took 3 minutes 17 seconds to complete our CS5 test in Windows, and 4:26 in Mac OS X. Again this is faster than the Mac Pro (4:42 in Windows; 4:59 in Mac OS). The Mac Pro does excel in one test, however: the more workstation-like CineBench test score in Mac OS (8.69) was higher that that of the iMac 27-inch (Thunderbolt) (4.86) due to the Mac Pro's ability to throw multiple processing streams at the CPU-intensive test. The Mac Pro has more pure CPU-based number crunching power than the iMac 27-inch (Thunderbolt), but the iMac 27-inch (Thunderbolt) was faster at day-to-day tasks that use other components like the hard drive and graphics.

With the help of site sponsor Other World Computing, the excellent BareFeats tested all four stock "Mid-2011" iMac models compared to "Mid-2010" iMac and Mac Pro models in synthetic benchmarks, Portal 2 gaming under Mac OS X, Windows games, and pro applications. Although all of the tests should be reviewed for the full perspectives, BareFeats was particularly impressed with the gaming performance of the "Mid-2011" iMac line, finding it to be a "best buy."

Finally, in perhaps the most comprehensive review of all, the superb AnandTech compared the stock high-end iMac "Core i5" 3.1 27-Inch (Mid-2011) to a number of Mac Pro, MacBook Air and MacBook Pro models from recent years and found the iMac to be faster than everything else in Aperture 2, single-threaded Cinebench R10 and Cinebench R11.5, and Quicktime X tests, but slower in others, particularly where multithreading is important.

Performance Summary

Ultimately, the "Mid-2011" iMac models provide significantly better performance than their predecessors across the board and can hold their own -- and even beat -- the "Mid-2010" Mac Pro line in tasks that do not benefit from multiple threads. Home users, "prosumers," and even many professional users are likely to be highly pleased with performance of the "Mid-2011" iMac line.

Site sponsor PowerMax has new 21.5" and 27" iMac models (as well as used iMacs) available for sale free of sales tax.

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