In an unexpected move, Apple has announced it will ship slower versions of its new Power Mac G4 computer than it had originally planned in August. The 500MHz system won't be introduced until the first calendar quarter of next year. The G4 lineup now includes models with 350MHz, 400MHz and 450MHz processors, which are priced at £1,099, £1,699 and £2,399, respectively.

Apple said last month that Motorola, which is manufacturing the G4 processors, had run into problems and wouldn't be able to keep up with demand for the chips. At the same time, Apple warned that the shortage would cut into its earnings for the quarter just completed.

"Despite receiving orders for over 150,000 (Power Mac G4) systems during the quarter, we were able to ship only 64,000 G4 units, which was far short of our plan," said Fred Anderson, Apple's chief financial officer.

Apple said that to help address the problem, IBM will begin manufacturing the G4 processors in the first half of 2000, giving Apple two suppliers.

The Power Mac G4 wasn't the only product for which Apple had trouble meeting demand. The company ended the quarter with "an extraordinarily large backlog" of more than 400,000 undelivered Macintosh systems, representing more than $700 million worth of business, Anderson said.

The company received orders for more than 200,000 iBook consumer portables during the quarter, but shipped only 6,000.

Apple warned when it introduced the iBook at Macworld in July that supplies would be limited. The shortage was compounded by a slower-than-expected manufacturing ramp, and last month's earthquake in Taiwan, which cost the company one week of production on both iBooks and iMacs at the end of the quarter.

Apple expects to catch up with the backlog on G4 desktops in November, although iBooks may remain in short supply throughout the quarter, Anderson said

Rumours from the States also indicate that Apple may be cancelling its pre-existing G4 orders. Apple UK state that this only affects orders for G4s in the 500MHz configuration.