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Intel's Pentium 4 'C' processors


There's room on the 800MHz bus for everyone
— 12:01 AM on May 21, 2003

TO GO ALONG WITH its shiny new 865 chipset family, Intel is bringing a new range of Pentium 4 processors to market at speeds of 2.4, 2.6, and 2.8GHz. These new Pentium 4 "C" revision chips include a pair of worthy enhancements: Intel's Hyper-Threading technology and support for an 800MHz front-side bus. Both of these changes promise to boost clock-for-clock performance on these new Pentium 4 chips, which should make a good thing even better.

Naturally, we wanted to see how these new CPUs match up to AMD's product lineup, as well as to past Pentium 4 chips, so we scraped together a whole pile of processors for some comparison testing. Will these new Pentium 4 chips leave AMD in the dust? Read on to find out.

The Pentium 4's new upgrades
Let's conduct a quick refresher course for those of you who have been watching Oprah instead of keeping up on your microprocessors (and we know who you are). We first covered the Hyper-Threading (HT) technology present in these new Pentium 4 "C" chips in our review of the Pentium 4 3.06GHz processor, which was the first P4 available with Hyper-Threading. HT is Intel's implementation of SMT, or simultaneous multithreading, in which a single CPU presents itself to operating systems as multiple processors. Scheduling multiple threads at once allows the Pentium 4 to keep its relatively long 20-stage main execution pipeline full, increasing clock-for-clock performance. At its best, Hyper-Threading even promises to inject some of that creamy smoothness familiar in multiprocessor systems into the user experience, for instance when one logical CPU is tied up with an antivirus check and the other one kicks in to keep other programs rolling.

Hyper-Threading does have its downsides, including some resource sharing, which we explored right here. Overall, though, we'd leave it turned on for our own use.

For the skinny on the 800MHz front-side bus, you will want to read our review of the Pentium 4 3.0GHz and Intel 875 chipset. You can also find out about the new 865 chipsets Intel is introducing today, which also feature an 800MHz bus, by reading our review of the 865 family.

Phew. That should get you up to speed.

Before we begin...
You will see one new addition to our CPU reviews this time around, which is a line graph that may be familiar to you from our graphics reviews. I was just playing around with these graphs and decided to include them here, because they kinda-sorta show how processors scale at different speeds and ratings.

That said, there's one big caveat you'll want to note. In throwing the processors into different classes or categories according to processor speed or "model number" rating, I had to fudge by 66MHz on both older high-end and low-end Pentium 4 chips: the "2600" is actually a 2.53GHz processor, and the "3000" actually runs at 3066MHz. Sorry, but those were my options. The net result of this situation is that the older Pentium 4 chips will appear to scale better on our graphs than they actually do. The "2600" data point will be a little low, and the "3000" data point will be a little high versus the new Pentium 4 "C" processors. Just keep that fact in mind, and all will be well. As you might expect, the new P4 "C" chips generally scale better with clock speed anyhow.