Apple interim CEO Steve Jobs ended weeks of speculation yesterday, with the announcement of the PowerMac G4 at Seybold in San Francisco. Jobs announced the new G4 processor as the "first supercomputer on a chip".

Running on a new chip developed by Apple, Motorola and IBM, the G4 incorporates a new execution unit, called the Velocity Engine - formerly known as AltiVec. The processor delivers over one gigaflop, or one billion, operations per second.

The G4 is available in three standard configurations, based on 400MHz, 450MHz and 500MHz processors. The two top models accommodate the Airport wireless technology that was introduced with the iBook at Macworld Expo in July.

They also have support for up to 1.5GB of fast PC100 SDRAM, Rage 128 AGP/2X graphics, an Ultra ATA/66 drive interface, and a new 100MHz system bus that delivers up to 800 Mbps throughput - twice the bandwidth of the PCI bus according to Apple.

All three models have 1MB level 2 backside cache, dual USB and 400Mbps FireWire ports, and internal drives from 10GB to 27GB. Removable storage includes ZIP, CD-ROM, DVD-ROM with video playback, and DVD-RAM.

In tests run by Intel, and published on the company’s Web site, the 500MHz G4 chip performed 2.94 times as fast as the 600MHz Pentium III processor.

Apple dropped the blue-&-white G3 design in favour of a silver, clear and graphite colour scheme, but retained the side door that swings open to access the insides. The Power Mac G4 400MHz costs £1,099, and will be available in the UK in September. The 450MHz G4 is priced at £1,699 and is scheduled to ship in early October, while the 500MHz model costs £2,399 and will follow in late October.