Apple imac 27-inch (2011)

As you'd expect, this top-of-the-range 27-inch 2011 iMac augmented by a processor upgrade excelled in our benchmarking tests. But with the entry-level 2011 iMac putting a performance that rivals the previous generation's most expensive model, does the average home user really need this much power?

Our Cinebench rendering test looks at how well the computer copes with complicated 3D graphics. Restricting it to a single processing core, this 3.4GHz Core i7 iMac proved just under 33.5% faster than its top-of-the-range predecessor.

Yet the entry-level 21.5-inch iMac in the current range beat the most expensive 2010 model too, proving almost 15% faster.

When all cores are used, the Core i7 chip's Hyper Threading feature comes into its own. With the rendering tasks spread over eight virtual cores, it proved over 62% faster than the top 2010 iMac, the 27-inch SSD, while the entry-level model in the 2011 range was almost 7% ahead.

In our QuickTime encoding test, we time how long it takes QuickTime 7 Pro to encode a five-minute, 720x480 sample video. This 27-inch Core i7 iMac completed the task in a very impressive 98 seconds, over half a minute faster than its 2010 equivalent's 131 seconds.

But the entry-level 21.5-inch iMac also proved quicker, encoding in 128 seconds. When testing the frame rate offered by the popular Mac game Doom 3, the entry-level 2011 iMac's 169.7 frames per second couldn't match the best 2010 model's 178 fps, but both were significantly behind the Core i7 iMac under review here, which achieved an excellent 244.3 fps.

In our Xbench test, which looks at the computer's CPU, memory and hard drive performance, it scored a very respectable 196.54.

Although this customised top-of-the-range 27-inch 2011 Apple iMac puts in an impressive performance, with the £800-cheaper entry-level 21.5-inch 2011 iMac holding its own against even the best 2010 model, is this this one worth the extra money?

Naturally, the 27-incher has more to offer over the sub-£1,000 21.5-inch iMac than just raw power. Its gorgeous 27-inch, LED-backlit IPS screen will certainly endear it to professional designers and video editors, as long as they're happy with its glossy finish. Apple still doesn't offer a matte option.

The 27-inch iMacs also have two Thunderbolt ports, while the 21.5-inch models only have one, and it's much better served by online customisation options, allowing you to add a bigger hard drive, a solid state drive, a better graphics card or up to 16GB of memory.

However, ordering extra RAM as a custom-order option is unwise. It's much cheaper if you buy from third-party vendors, and easy to fit it yourself.

Given the performance of the entry-level 21.5-inch 2011 iMac, you have to ask whether it's worth paying so much more for this top-end model. Perhaps the cheaper iMacs are now so powerful, the pricier releases struggle to find their niche with the home user.