posted by Nicholas Blachford on Mon 15th Jul 2002 01:14 UTC
IconAccording to a brief paragraph on MacOS Rumours Apple may be switching to IBM POWER4 CPUs instead of the Motorola G5 for future Macs.

Editorial notice: All opinions are those of the author and not necessarily those of

The quote reads:

"Also, Apple sources have recently told Rumours that when Apple ships computers branded as PowerMac G5s next year, they will almost certainly not include Motorola PowerPC 8500 processors, which are the G5 as we know it today -- they will be IBM-built chips based on its Power4 architecture, and may even include multiple cores on a single chip. More on this after Macworld...."

With constant complaints about the performance of the current crop of G4 CPUs a new faster CPU is needed and soon, while a speed bump to the current top end PowerMacs is due soon they will still be outperformed by the current top end x86 CPUs from Intel and AMD.

Apple appear to be looking to take ground from UNIX vendor SGI in the Audio / Visual fields however SGI use MIPS 64bit Rx000 CPUs for which the G4 is likely not a match, especially on intensive floating point which workstation CPUs specialise in.

If Apple have chosen instead to use IBMs POWER4 CPUs in the future they couldn't have made a much better choice if they want performance.

Currently the POWER4 ships in a multi-CPU module consisting of 4 chips and a separate L3 cache. Each chip contains 2 individual POWER4 CPUs. They don't however need doubling up to provide performance - In Spec SFP2000 benchmarks a single POWER4 CPU at 1.3GHz outperforms Pentium 4 at 2.53GHz by about 40% (1266 Vs 901).

IBM have already announced they plan to make single chip POWER4s available in their own workstations, Apple using the chip isn't surprising, It uses the same PowerPC instruction set and IBM have been making G4s since 1999/2000.

It won't all be plain sailing though - The POWER4 is a big expensive chip although a shrink to 0.13um will help here along with providing a significant frequency boost (2GHz+ is already on IBMs roadmap). POWER4 also consumes copious amounts of power unlike the current G4. Just don't expect a POWER4 notebook any time soon...

What remains to be seen is how will the Altivec vector instructions be used? This is a big selling point for Apple so it's possible IBM may be planning to include a vector unit in a future version of the POWER4.

So what of the Motorola G5? The 8500 is really only an enhanced G4, the "real" G5 is the 7500 with an extended 13 stage pipeline and already rumoured to reach 2.5GHz. Motorolas main market is Embedded CPUs so it's likely the chip will still come to market but if the above story is true it may not appear in Apples flagship products. However that wouldn't rule it out from appear in lower and mid range products at some point in the future.

About the Author:
Nicholas Blachford is a Software Engineer / Architect currently living in Amsterdam. He has numerous geeky interests including CPUs.

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