The pre-Macworld Expo rumour mill is humming with reports that G5 Power Macs could appear in San Francisco in January.

Reports from The Register, and repeated on Web sites worldwide, strongly suggest that a G5-based product could be announced. The report claims Apple's G5 products may feature speeds of up to 1.6GHz. It also predicts Apple will introduce a faster implementation of FireWire, with Double Data Rate RAM (DDR RAM), a fast system bus and up to 512K of on-die cache. Predictions from other sources posit the introduction of USB 2.0 and a much improved motherboard architecture.

However, other industry sources suggest that introduction of G5 Macs could be preceeded by a new generation of faster G4s.

G4 potential In an attempt to add facts to the rumours, Macworld contacted Motorola. The company's sources are reluctant to discuss the possibility of such plans. "Apple is an important customer, and, as with all our customers, we extend the courtesy of allowing it to announce products built using our solutions," said Paul Clark, Motorola's European marketing communications manager.

Conceding that work on the G5 chip is progressing "well", Clark warned that Motorola "doesn't want to fan the flames of expectation".

"There's only one announced product built on the E500 core that's at the base of G5s," Clark explained. Announced at the Microprocessor Forum in San Jose in October, this is an embedded product (the MPC 8540) designed for high-speed networking applications.

Chip convergence Clark also explained that Motorola is beginning to build features into its microprocessors that support communication as well as computing functions – "reflecting the increasing convergence between communications and computing", he explained.

Motorola will deliver a G5 chip "at some point", said Clark. He confirmed that G5 features will include a Rapid Input/Output architecture, and 32-bit and 64-bit backward-compatible chips. These microprocessors will be built using Motorola's 0.1-micron silicon-on-insulator (SOI) technology. Motorola expects to reach 2GHz capacity with these chips "at some point", he said.

G4 future However, Clark wanted to mollify speculation of a G5 Mac, pointing out that the potential of the G4 architecture has "exceeded Motorola's initial expectations". He said: "The G4 has a great deal of remaining potential. There's a great deal of headroom left in the chip, which still has enormous usability." Cisco Systems has adopted G4 chips for some of its networking products already, he told Macworld.

He praised the G4's asymmetric multiprocessing features. "This is extremely useful," he said, "and not just for Apple." He confirmed that G4s are expected to max out at speeds of about 1GHz.

Clark's message to Macintosh users was simple: "We don't want to raise people's expectations beyond what's possible. We will not discuss how or when customers, such as Apple, are applying our technology."

Apple UK wouldn't comment on the topic. "We do not comment on industry rumour," said Apple PR David Millar.

Macworld Expo San Francisco, 2002, runs January 7-11, with a keynote speech on Tuesday, January 8. Apple traditionally discusses its strategy for the year and makes major product announcements there.