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Intel's Pentium D 820 and Pentium 4 670 processors the 945G chipset

IT'S THE GEEKY equivalent of a conversation that most guys would have about a Maxim girl versus the Olsen twins. Would you rather have a single, very fast CPU or a pair of somewhat slower processors? That's a tough question, and it's precisely the one that Intel has prompted by releasing a couple of new CPUs today, the Pentium D 820 and the Pentium 4 670. The P4 670 is the fastest single Pentium 4 processor ever released, running at nearly 4GHz. The Pentium D 820, meanwhile, runs a full gigahertz slower, but it has two complete Pentium 4-style CPU cores onboard for a very nice price.

Which is better? Well, that depends on a great many things. Let's have a look at some of them.

Two new Pentiums roll out
In many ways, the two CPUs Intel is introducing today are fundamentally similar. Both are based on the latest version of the Pentium 4's Netburst microarchitecture, both ride on an 800MHz front-side bus, and both are capable of 64-bit computing via Intel's EM64T extensions. But beyond these wide areas of overlap are deep differences in approach.

The Pentium D 820 (left) and Pentium 4 670 (right)

The Pentium 4 670 is arguably the last of an old guard, a CPU intended to extract maximum performance out of a single processor core. The P4 670 extends the familiar Pentium 4 600 series one more speed grade, to 3.8GHz, and like the rest of the 600 series, the P4 670 packs 2MB of onboard cache to further improve performance. For the privilege of owning a CPU that runs at this dizzying speed, you'll have to pay something close to Intel's list price of $851.

The cores on the Pentium D 820 pulse along at a relatively leisurely pace of 2.8GHz, but there are two of 'em, so its overall performance in multithreaded applications or when multitasking may be superior to a single-core CPU. We've already reviewed the Extreme Edition of Intel's dual-core desktop chip, code-named Smithfield. The Pentium D is a de-tuned version of the Smithfield core that's had its Hyper-Threading capabilities disabled and its clock speed dialed back a few notches to 2.8GHz. In fact, its clock speed is sufficiently slow that Intel apparently saw no need for the 820 to have power management features like Enhanced Speedstep, the C1E halt state, or TM2 thermal throttling. Other recent Pentium desktop processors run at 2.8GHz when throttled back, and the Pentium D 820 is already there.

The real virtue of the Pentium D 820 isn't just its dual processor cores, though; it's the price. At only $241, the Pentium D 820 signals that Intel is dead serious about bringing dual-core CPUs to desktop PCs. In fact, the Pentium D's price is low enough to shake up the whole CPU market. Its arrival presents consumers with a series of stark choices between single-core and dual-core processors at roughly comparable prices.

That fact, combined with the proliferation of very different model numbering systems from AMD and Intel, has made head-to-head competitive comparisons of CPUs quite a bit trickier than in the past. Freed from the constraints of model number-clock speed comparisons, Intel and AMD have priced their CPUs at points that don't entirely correspond to one another. I've made an attempt, in the table below, to classify competing CPUs in a reasonably direct manner, but I may have only succeeded in illustrating the problem.

CPU Price CPU Price CPU Price CPU Price
Pentium 4 630 $224 Athlon 64 3200+ $194
Pentium 4 640 $237 Pentium D 820 $241 Athlon 64 3500+ $272
Pentium D 830 $316
Pentium 4 650 $401 Athlon 64 3800+ $373
Pentium D 840 $530 Athlon 64 4000+ $482 Athlon 64 X2 4200+ $537
Pentium 4 660 $605 Athlon 64 X2 4400+ $581
Pentium 4 670 $851 Athlon 64 FX-55 $827 Athlon 64 X2 4600+ $803
Pentium 4 XE 3.73GHz $999 Pentium XE 840 $999 Athlon 64 X2 4800+ $1001

That's official pricing on the Pentium D line, by the way.

You can see the trouble. Identifying a direct competitor for some of these models, like the Pentium D 830 or the Athlon 64 4000+, is downright befuddling. Fortunately, the two processors we're reviewing here line up fairly directly against the competition. The Pentium 4 670 is priced pretty close to the Athlon 64 FX-55, and the Pentium D 820 just undercuts the Athlon 64 3500+ by $31. That means, of course, that the Pentium D 820's two somewhat pokey cores will do battle with a relatively quick single-core competitor from AMD.

This is what I meant by stark choices. AMD doesn't offer a low-end dual-core processor and apparently doesn't plan to do so in the near future. For many single-threaded tasks, one of the Pentium D 820's 2.8GHz cores should be sufficient, but it's hardly quick by current standards—especially when you consider that the long pipeline of the Prescott/Smithfield cores means lower clock-for-clock performance. Intel also offers the Pentium 4 640 at the same basic price, but there's no way a single-core Pentium 4 at 3.2GHz can match the Pentium D 820 overall. I'm getting ahead of myself, though. We'll let the benchmarks tell that tale.