IBM last night made additional details regarding its PowerPC 970 public.

The company released formerly limited circulation excerpts from October 2002's Microprocessor Review to selected media outlets, including Macworld UK.

The report, written by senior editor Tom Halfhill, confirms some details about the chip that have been circulating through the Internet.

Halfhill said he found it 'hard to imagine' that Apple would use anything else in its desktop Macs and servers."

The report begins: "Nobody at IBM would confirm rumours that a leading customer for the PowerPC 970 is Apple - and Apple is even more tight-lipped. Nevertheless, the 970 is such an obvious improvement over today's Motorola G4 family PowerPC chips that it's hard to imagine Apple using anything else in its desktop Macs and servers."

Claiming the chip to be "tailor-made" for professional publishing and media-processing applications, the report confirms: "It has 64-bit datapaths and memory addressing, yet it's natively compatible with 32-bit PowerPC software."

Additional features confirmed within the report include: a deeper data pipeline; bus rates of 900MHz; data bandwidth of 6.4GB/s; AltiVec. The PowerPC has 52 million transistors and is a stripped down version of IBM's Power4 processor, used in large-scale server installations.

"The deeper pipeline is especially welcome because it could allow the 970 to reduce the growing clock-frequency gap between today's PowerPC chips and the speedy x86 competition."

Calling Motorola's G4 and G4+ data pipelines "stunted" in comparison to Pentium 4, Halfhill suggests that initial estimates of 970 processor speeds are "conservative". In October it appeared the chips would offer speeds of 1.2-1.8GHz.

The report reveals the 970 to offer a 16-stage pipeline - 9 more than the G4+ and 12 more than the G4 and G3 processors. The processor offers two built-in floating point units, AltiVec support, a 64K L1 cache with a 512K L2 cache and a front side data bandwidth (FSB) of 2 x 3.2GB/s. The G4+ offers a 1GB FSB.

The FSB is the part of the processor that allows data to be moved from memory into the processor to be manipulated, and back again.

"The PowerPC 970 is clearly in a different class than existing G4+, G4 and G3 PowerPC chips. Its deeper pipelines and much faster FSB fix the most serious shortcomings of today's PowerPCs."

Looking at the history of the AIM (Apple, IBM, Motorola) alliance, the report says: "In fact, a 64-bit PowerPC was planned right from the start, when IBM, Motorola and Apple began creating the PowerPC architecture in the early 90's, the alliance promised to deliver three 32-bit processors - the 601, 603 and 604 and one 64-bit implementation, the 620."

The latter chip was never used on a Mac, but the inherent architecture of the PowerPC has always supported 64-bit memory addressing.

Execution is significantly faster - the 970 can fetch up to eight instructions per clock cycle, can dispatch up to five instructions per cycle to the function units, issue up to eight instructions per cycle and retire results for up to five instructions per cycle. "The 970 can juggle an unusually large number of instructions in its piopelines," Halfhill writes.

The FSB implementation is crucial. The processor drives this at up to 900MHz. The Pentium 4 offers 533MHz and the Athlon XP gets 333MHz.

The report offers several comparisons with competing processors, and the 970 seemingly surpasses or competes with x86-based competition. Its adoption would help Apple remain competitive in the market.

Halfhill concludes: "It's a good bet the 970 will also end up in a Mac - unless Apple's thinking is even more different than advertised."

Online, Mac rumour sites have begun to claim 970 processors are already arriving with manufacturer's in the Far East - who are working for a client called Apple.

Apple does not comment on rumour or unreleased products.