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Macs aside this CPU is mainly targeted at embedded applications so it's presence for the most part will not be visible. It will turn up in some desktop systems though, for general consumer computing the existing G4 provides more than enough computing power so a pair of them at a higher speed with much faster memory should provide quite a potent system for that market.

There has been no official announcement but Genesi have said their future products will track Freescale CPU development and my information is they do indeed plan to use this processor at some stage in the future.

Conclusion
The 8641D may not get the single threaded performance of high end PC chips but it's not designed for that, having said that this CPU will probably deliver the majority of that level of performance even if it doesn't quite reach 100%. The clock rate is highly deceptive as CPUs spend much of their time sitting around waiting for data so raising the clock rate doesn't necessarily translate to an equivalent level of higher performance. The Itanium II CPU (also at 1.5GHz) with 6.4GBytes / second memory bandwidth and a huge 6MB cache has been studied and even when running a highly optimised benchmark is doing absolutely nothing for 50% of the time - and that's one of the world's fastest CPUs (i.e. it'll happily eat any x86).

On the desktop bragging rights matter, they are completely irrelevant in the most of the embedded world if you can't perform in a low power budget. An extra 10-20% performance isn't so as important as to be worth the additional effort and cost. A dual core PC CPU may be faster than this on raw computing speed but don't expect to see them in many embedded systems any time soon.

The already high power consumption of single core PC processors means manufacturers will have to lower the clock of the CPU cores otherwise a pair will use far too much power and end up approaching 200 Watts, AMD are doing exactly this with the dual core Opteron, they will run 3 or 5 speed grades below the top single core Opteron. Freescale have a lot more headroom so don't need to do this, they can run both cores at full speed and still come in at less than half the power consumption of other PC CPUs. This problem will also affect the G5 unless IBM can lower it's power consumption, currently a dual 1.8GHz G5 should be possible at under 100 Watts (Maximum).

It's clear to me in some respects that the embedded and desktop markets are converging in this CPU, Freescale have been shipping highly integrated CPUs for years now but they've never appeared anywhere near desktop systems. PC CPUs wont be able to race away from embedded CPUs as they have over the last few years, if anything I think the gap will tend to close as everyone starts using multiple cores.

The 8641D and other family members are targeted at a different market from PC CPUs so direct comparisons are not terribly meaningful unless you're interested in using one as a desktop. PCs are upgraded at a rapid pace, the current top end is often a few notches down within a few months if not sooner, within a couple of years they're not even being made any more. In the embedded world you expect these parts to be on sale and in use for many years. I bet there's not many people still using 10 year old CPUs in their main system, would many of those systems even work now these days? The 8641D is expected to be around for a long time - it's got a reliability rating of 10 years at 105¡C.

What if?
Freescale didn't need to drop the speed of their cores to put two on a single die but if they did they could build some very potent processors. Dropping the cores to 1.4GHz should allow 4 cores to be used and still remain under 50 Watts. They could even build an 8 core device if they wanted and still stay under 100 Watts, it would outgun every PC CPU on the market several times over and still not use as much power as a P4 Prescott!

Perhaps the criticism levelled at the G4 should have been sent in another direction...

© Nicholas Blachford, October 2004