The developers appear less than impressed with the raw performance of the PPE unit(s) in these CPUs. They also say the SPE units in the PS3's Cell CPU are difficult to use in game code.
Right now, from what we’ve heard, the real-world performance of the Xenon CPU is about twice that of the 733MHz processor in the first Xbox. Considering that this CPU is supposed to power the Xbox 360 for the next 4 - 5 years, it’s nothing short of disappointing. To put it in perspective, floating point multiplies are apparently 1/3 as fast on Xenon as on a Pentium 4.Even though much of the article should be considered speculation since it does not contain any hard data (partially because the hardware hasn't even been officially released yet), we should not be surprised that some developers feel this way, given the differences in the designs of these chips from current general purpose CPUs. Nonetheless, it's not surprising that Apple's engineers chose not to use Cell in the Mac.
The reason for the poor performance? The very narrow 2-issue in-order core also happens to be very deeply pipelined, apparently with a branch predictor that’s not the best in the business. In the end, you get what you pay for, and with such a small core, it’s no surprise that performance isn’t anywhere near the Athlon 64 or Pentium 4 class.
The Cell processor doesn’t get off the hook just because it only uses a single one of these horribly slow cores; the SPE array ends up being fairly useless in the majority of situations, making it little more than a waste of die space.
[Update 2005-06-30]
We now have an explanation as to why the article was pulled: "PS3 article is pulled for now because Anand is worried about MS tracing his anonymous insider."
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