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IBM lays desktop PowerPC on Cupertino lawn

Who else could want it?

IBM is to release a version of the dual-core Power4 processor aimed at the desktop, and will disclosed details at Microprocessor Forum in October.

The new chip designed for "desktops and entry level servers", and will be an 8-way superscalar, SMP-ready design capable of 6.4GB/s throughput. Tantalisingly, the processor has it own "vector processing unit implementing over 160 specialized vector instructions."

The "over 160" number is quite significant: the AltiVec vector unit for the PowerPC G4 has… 162 instructions.

Now why would IBM want to do create a desktop RISC processor? It needs to remain competitive with entry-level workstations against the likes of Sun and HP's Alpha, where the size and heat dissipation of the mighty POWER4 have kept it out of systems below $12,000. IBM's desktop workstations still run POWER3 (but then you can find UltraSPARC Iis in Sun's bargain basement).

However AIX and OS/400 are not the only PPC-compatible operating systems out there. There is of course, Apple's Mac OS X, potentially a significant volume addition for Big Blue - at least in terms of volume as the UNIX big iron world know it.

IBM and Motorola designed the Book E specification together, which forms the basis for Motorola's G5. So the two largest partners of the old AIM (Apple, IBM and Moto) alliance still work closely.

With the Alpha destined for the scrapyard, POWER4 looks set to remain top of the performance heap for several years, giving Apple's professional users all the, er power they need. But the move could run into two problems. Firstly, Apple has "tied the future" of the company's hardware to AltiVec. And so have professional media application developers. If the vector unit in the desktop Power4 isn't AltiVec, it may be useless to Apple.

Secondly, it requires a great deal of imagination to see today's POWER4s in low power notebooks. Motorola effectively threw in the towel with volume desktop processors five years ago by focussing on embedded applications. But what has been pro users loss has been notebook users gain: this is a highly profitable part of the Apple business, and given the less than spectacular sales of the Cube and the iMac2, is an area where Apple has consistently seen growth. Despite the efforts of Transmeta, the only notebooks you'll find in CompUSA with five hour battery life (enough for a coast to coast flight in Apple's biggest market) are Apple notebooks.

Apple wouldn't want to bifurcate its roadmap between G3/4 and POWER4 for desktop/server and notebook: but it knows how to. The NeXT team who took over Apple in 1997 have plenty of experience of producing one binary for different processor architectures: HP-UX, Solaris and x86 as well as Mach on 68000. NeXT called these Multi-Architecture Binaries, or MABs.

One glitch in what could be a smooth transition could simply be the amount of legacy MacOS9 code: much of 'Classic' is still written in 68000 instructions. Getting OS X onto a new processor is going to be difficult with so much old code hanging around.

This week Matt Rothenberg and Daniel Drew Turner wrote a fascinating report at eWeek suggesting that new Macs next year won't be able to run the old MacOS.

Could this be why? ®

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