Intel’s P4(E): Prescott
AnandTech has a very lengthy and in-depth article up today about Intel’s newest chip, the Prescott core Pentium 4. This chip will be differentiated from previous versions with the “E” designation, so a 2.8GHz Prescot core will be a “Pentium 4 2.8E”. For those who aren’t aware, pretty much all the common desktop chip type go through occasional revisions where they receive new features and such but still retain the same overall identifier, such as “Pentium 4” or “Athlon”.
Anyway, I don’t normally comment on stuff like this because it simply isn’t that interesting to most people, even though I do find it interesting myself. However, in this case I thought some of the changes that Intel made to the Prescott version were quite interesting. Read on to find out some of the details and what they mean.
First off, Intel increased the pipeline in the processor from 20 to 31 stages, which is a 55% increase. A longer pipeline lets the processor reach higher clock speeds (i.e. more GHz) but also means that it does less per clock. So all other things being equal, a 2.8GHz ‘Prescott’ core will be slower than a 2.8GHz P4 based on the previous core ("Northwood").
Another major change with Prescott is that Intel doubled the size of one of the main memory caches on the processor. Usually, that would be excellent news and would go a long way to help offset some of the drawbacks that come with the longer pipeline mentioned above. In this case, though, the cache used in Prescott is slower (actually, the access to the cache is slower) than in previous versions, so that means the increased size of the cache is largely irrelevant as far as increasing performance goes.
So, we have two big changes to the Pentium 4 core that basically make it slower than the previous version. Doesn’t sound good, does it? Well, Intel was obviously quite aware of what they were doing, so they also made lots of other improvements that essentially try to “make up” for this other loss in performance. According to the AnandTech article, they’re largely successful in their efforts: in most tests, Prescott is only slightly slower than the previous version of the Pentium 4 core.
By now you’re probably wondering what the heck Intel was thinking. Well, what the changes they made do is allow for much greater headroom for the new processors. With the Prescott core Intel expects to be able to reach about 5GHz by the end of next year. (I think we all know how Intel seems to think putting out higher numbers can be more important than actually putting out better performance. Then again, who’s to blame them since Joe Consumer is certainly more likely to think that a 3GHz Pentium 4 must be better than a 2GHz Athlon 64 or G5 even though that certainly isn’t the case.) Also, while the newly released processors (which are the same speed as those of the previous version) actually perform slightly worse than the Northwood cores in most things, the Prescott performance ramps better than Northwood as its speed increases.
So, basically, in the future Prescott will be better, but right now you’d be a sucker to buy it instead of the existing version. Kind of weird, huh?
Of course, for most—or at least many—things the currently available Athlon 64 processors will probably perform better. Then again, I’ve always been a fan of AMD ever since the Athlon came out…
Posted Monday February 2, 2004 in News by Chris Curtis
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