After more than two years, Motorola Inc., late last week revised its road map for the companys PowerPC processors, the chips that lie at the heart of many embedded devices as well as Apple Computer Inc.s Macintosh computers.
Though the new information is slight, for many it reinforces speculation that Apple will release new desktop computers based on Motorolas “G5” family of processors, perhaps as early as Januarys Macworld Expo/San Francisco trade show, sources said.
Some purported features of the new G5 family (initial models will carry the PowerPC 8500 moniker) remain unchanged from a 1999 version of Motorolas road map. These include an extensible architecture; a new pipeline and bus topology; and both 32-bit and 64-bit versions with backwards compatibility. (Read about what Motorola engineers did on their summer vacation.)
However, the new road map does highlight some revised aspects to the G5 family. New features include the adoption of the RapidIO Interconnect Architecture and symmetric multiprocessing capabilities (first seen in the PowerPC family with the G4 processor). Other revisions are initial speed estimates of 800 MHz to 2+ GHz (as opposed to past estimates of 2+ GHz to start) and a 0.13 micron manufacturing process instead of a 0.10-micron process.
The RapidIO Interconnect Architecture is described on Motorolas Web site as a new technology, overseen by the non-profit RapidIO Trade Association (of which Motorola is a member), for increasing bandwidth and chip-to-chip communication speeds. This dovetails with reports that new Macs could feature bus speeds of up to 400 MHz.
RapidIO is “ready to go,” said Peter Glaskowsky, a senior analyst and senior editor of the San Jose, Calif.-based Microprocessor Report. He noted that RapidIO is a technology Motorola has been making great strides in and that it could serve not only to achieve the rumored 400MHz bus speed but also to increase overall performance of a RapidIO-equipped computer.
It could also serve to improve performance in multiprocessor systems, Glaskowsky said. “Each processor could have its own channel into the memory controller and the memory controller could keep both channels running at full speed at the same time,” he said. Apple has been offering at least one multiprocessor desktop system in its lineup in recent years.
As for the apparent decrease in initial G5 chip speeds represented in Motorolas new road map, Glaskowsky said that could indicate “some sort of power-optimized version,” possible for a mobile application such as a laptop computer, he said. And, he added, he would have been surprised if Motorola had been able to implement a 0.10-micron process this early; the 0.13-micron technology is far more mature, he said.
Overall, Glaskowsky said, this information was “consistent” with reports he had been hearing of Apple announcing G5-based computers at next months Macworld Expo. Even if, he said, other reports, about Macs badged “G5” but sporting a PowerPC 7460 chip — previously considered part of Motorolas G4 generation — pan out. The PowerPC 7460, carrying the code name Apollo, has not yet shipped in any Mac model.
Apple representatives stated that it is their policy not to comment on unreleased products.
“The chips now shipping [in Macintosh systems] are what Motorola was calling G5 a few years ago,” Glaskowsky noted. The current G4 processors, he said, have more pipeline stages and “a better core” than previous versions; this change, he said, was more significant than the change between Intels Pentium II and Pentium III processors. The Pentium III offered no microarchitectural changes yet rated a name upgrade, he said.