Apple's new 2011 iMac range retains the form factor of the 2010 models, but enjoys a very significant component upgrade. Second-generation quad core Intel Core i5 processors are used throughout the 2011 iMac lineup - which includes two 21.5-inch models and two 27-inch models - where previously all but the most expensive model had dual Core i3s.

New graphics give up to three times the power of the mid-2010 iMacs, and the Thunderbolt port could revolutionise I/O technology.

The 2011 21.5-inch iMac reviewed here is the new range's entry-level model, costing £999. It offers a quad core Intel 2.5GHz Core i5 processor, a great leap forward from the dual core 3.06GHz Core i3 used in the cheapest 2010 release.

Its discrete graphics chip is a powerful AMD Radeon HD 6750M, with 512MB of GDDR5 memory, up from an ATI Radeon HD 4670 with 256MB of GDDR3 RAM.

The Mini DisplayPort has been replaced by a Thunderbolt port, Intel's exciting new I/O technology that can support up to six daisy-chained peripherals and data transfer speeds of up to 10Gbps in both directions. It's over 20 times faster than USB 2.0 and 12 times quicker than FireWire 800.

Thunderbolt also supports video, and can be used to connect an external monitor. It can even function as a video-in port, allowing you to use the iMac's gorgeous 1920x1080 pixel 21.5-inch LED-backlit glossy widescreen display as a screen for another device. The SD card reader is retained, but it now accepts SDXC cards for a theoretical maximum capacity of 2TB, with cards of up to 64GB already available.

For those who like video chat, the built-in webcam has been upgraded to a FaceTime HD camera, giving 720p resolution, a 16:9 aspect ratio and a much-improved low-light performance. Yet despite these improvements, the entire range is now cheaper than before. Not hugely so, but this particular model is £21 cheaper than its predecessor.