Another round of frenzied speculation is over - Apple has announced an all new family of iMac desktop computers. As widely predicted, the big change is a swanky new anodised aluminium and glass enclosure. However, the new machines make no concession to Apple's preferred HD disc format, Blu-ray, while the range also boasts a new high end Intel dual-core chip.

The latest iMac retains similar overall proportions and compact all-in-one design as the outgoing system. However, it will only be available in two sizes: 20- and 24-inch. The entry-level 17-inch iMac is history.

At the launch event in California, Apple supremo Steve Jobs said the upgrade to glass and aluminium was a logical for the new iMac. According to Jobs, the new materials are not only more elegant. They also offer improved scratch resistance and are more recycling friendly. And we wouldn't argue.

The revised systems receive a comprehensive technical overhaul including upgraded CPUs and 3D chips plus a brand new pair of keyboard designs.

Leaner, meaner

Overall, the new iMac is slimmer, cheaper and boasts more powerful dual-core CPUs than the outgoing model. UK prices kick off at £799 for the new entry-level model powered by an Intel Core 2 CPU running at 2GHz. An upgraded 2.4GHz 20-inch model is yours for £949, while the 24-inch model with the same CPU starts at £1,149. The range topping 24-inch iMac, meanwhile, lists at £1,459 and sports a new 2.8GHz Intel Core 2 Extreme processor.

All the usual iMac accoutrements, including a full compliment of USB 2.0 and Firewire 400 / 800 ports, integrated iSight camera, Bluetooth and AirPort Extreme wireless networking also make an appearance. Standard hard drive capacities range from 250GB to 500GB with up to 1TB available on the 24-inch iMac.

Bereft of Blu-ray

Conspicuous by its absence, however, is support for the latest high definition video disks. Apple may have placed its flag in the Blu-ray camp. But for now its customers must wait. A Blu-ray drive is not even offered as an option. Both 20 and 24-inch models boast what Jobs described as "glossy" LCD displays. Jobs reckons "customers love" glossy screens, an observation that probably reflects feedback from the MacBook laptop.

However, until we get a chance for a closer look, it's not clear whether the "glossiness" Jobs has referred to is due to the glass screen cover or whether the screen surface itself is glossy, too. Either way, early images taken at the launch event suggest the latest iMac's screen suffers from distracting reflections.

Internally, the new iMacs are powered by CPUs and chipsets closely related to the latest Intel mobile clobber. Specifically, that means Core 2 processors with 800MHz CPU buses - most of Intel's current desktop chips boast bus speeds of at least 1,066MHz. System memory likewise takes the form of laptop-spec SO-DIMMs humming a 667MHz tune.

Intel intrigue

The Intel mobile connection also explains the slightly odd labelling of the top model's processor. Currently, Intel does not publically offer a 2.8GHz Core 2 Extreme PC-compatible CPU in either desktop or mobile trim. However, it's likely the chip is a minor revision of the recently released 2.6GHz Core 2 Extreme X7800 notebook processor.

As for graphics, Apple has chosen ATI's new entry level and midrange DirectX 10 3D chips. The basic 2.0GHz 20-inch model makes do with the rather weedy Radeon HD 2400 XT in 128MB trim. The remainder of the range receives the more powerful Radeon HD 2600 Pro with 256MB of video memory.

Finally, the latest iMac is accompanied by a pair of new keyboards. A full width wired keyboard with numeric keypad comes as standard. Optionally, Apple offers a new compact Bluetooth wireless unit. Both share the same design vibe: an ultra thin silver chassis topped with an array of white keys. Ergonomically, they're a dead ringer for the keyboard fitted to Apple's MacBook consumer laptop. In other words, flat, square and relatively widely spaced keys with restricted throw.

The new iMacs are available now from Apple's online store . Keep your scanners peeled for Tech.co.uk's full upcoming review.

The rumours were right: Apple's latest iMac receives a slick new aluminium enclosure