UPDATE: Check out our latest 27-inch Apple iMac review

Although the form factor is unchanged, the 2011 Apple iMac refresh represents a significant step forwards for the popular all-in-one computer. Again consisting of two 21.5-inch models and two with 27-inch screens, the entire lineup has switched to Intel's Sandy Bridge processors, the second generation of the respected Core-i CPU series.

Quad core Intel Core i5s are used throughout, whereas the 2010 iMacs they replace used dual core Intel Core i3s in all but the most expensive model.

Our colleagues at T3.com grabbed some Apple iMac 27-inch footage which you can watch below.

The 27-inch iMac under review here is the priciest in the 2011 range, but instead of the quad-core 3.1GHz Intel Core i5 processor offered in the standard configuration, ours was fitted with a quad core 3.4GHz Core i7 CPU. This is available as a configure-to-order option on the online Apple store, costing £1,809 rather than the £1,649 quoted for the top-end off the shelf offering.

It's otherwise identical to the top-of-the-range 27-inch 3.1GHz iMac in the 2011 range. Its graphics processor is an AMD Radeon HD 6970M with 1GB of GDDR5 memory, up from an ATI Radeon HD 5750 in the top 2010 version, the 27-inch SSD.

Storage remains unchanged – a 1TB 7200rpm hard drive is installed as standard, with configuration options offering a 2TB drive, a 256GB solid-state drive or a combination of SSD and HDD.

Once again, it has 4GB of 1333MHz DDR3 memory out of the box, which can be expanded to 16GB either as an online configuration option or a post-market modification by the end user.

The 27-inch 2011 iMac's Mini DisplayPort has been dropped in favour of two Thunderbolt ports, an exciting new I/O technology that can support video as well as data.

You can plug a Mini DisplayPort monitor directly into a Thunderbolt port for use as a second screen, and it also acts as a video-in port, allowing you to use the iMac's huge 2560x1440 pixel 27-inch LED-backlit glossy widescreen display as a screen for another device.

The FaceTime camera has been upgraded to HD, and the SD card reader now supports the SDXC format.