OVER THE PAST FEW weeks, we've seen a parade of dual-core CPUs, starting with the Pentium Extreme Edition 840 and the dual-core Opterons. Now it's time for AMD's dual-core desktop processor line, the Athlon 64 X2, to take its turn on stage. Sporting a fashionable 939 pins on their underbellies, these CPUs promise to drop into the average Athlon 64 desktop system and transform it, almost magically, into a dually. The X2 offers an infusion of creamy multitasking smoothness and nearly twice the peak processing power of an Athlon 64 FX-55.

We've had two versions of this CPU on the bench in Damage Labs for a while now: the screaming 4800+ that may be the fastest single microprocessor on the planet, and the gotta-have-it 4200+, AMD's most affordable dual-core processor that promises to be every enthusiast's new sweetheart. Can AMD's dual-core desktop processors deliver on their promise? Keep reading.

Introducing the X2
As you might expect, the Athlon 64 X2 is simply the desktop version of the dual-core Opteron that we reviewed recently. It's the same basic chip, just in a different package. In fact, the package will look very familiar to those of you who have seen a Socket 939 processor before. Here, in keeping with TR tradition, are a couple of big pictures of the CPU.

AMD says the Athlon 64 X2 should fit into existing motherboards with only a BIOS update, provided that the motherboard can deliver enough power to drive a current 90nm Athlon 64 processor. Existing Socket 939 CPU heat sink/fan combos should be sufficient to cool an X2, as well. As always, you'll want to check with your motherboard maker before assuming your mobo will work with the new chip. There are always exceptions.

Given the performance of the dual-core Opterons, the X2's common heritage should come as heartening news. The desktop version of AMD's dual-core processor will come in four flavors featuring two different clock speeds, 2.2GHz and 2.4GHz, and two L2 cache sizes, 512K per core and 1MB per core. The entire lineup will look like so:

The X2 line will range from expensive to painfully expensive to root-canal-without-anesthetic expensive. Unlike Intel, AMD will not initially be offering a relatively cheap dual-core processor that steps on the toes of its current single-core offerings in the meaty part of the market. All of the X2 chips are priced above the Athlon 64 4000+, and they get higher model numbers, as well.

Speaking of model numbers, AMD has apparently foregone a perfect opportunity to throw out its "clock speed equivalent" rating system that's increasingly less relevant over time—especially now that dual cores are the order of the day. Take the Athlon 64 X2 4800+, for example. The 4800+ is literally a pair of K8 cores running at the same clock speed as a single Athlon 64 4000+, but it only gets a model number increment of 800. Too modest? Perhaps, but who's to say? Does a bear pope in the woods? A question can be hard to answer when it makes no sense. AMD would have done well to abandon its True Performance Initiative now that the shift to thread-level parallelism has thrown clock speed-based performance estimates out the window once and for all. Somehow, the company that once looked like it was tilting at windmills trying to get Intel to acknowledge that clock speeds aren't a faithful indicator of CPU performance continues to beat on the windmill now that it lies broken on the ground.

Anyhow, the price-competitive scenarios between Intel and AMD CPUs look like this. The Athlon 64 X2 4800+ will match up directly against the Pentium Extreme Edition 840 at about a thousand bucks, while the X2 4200+ will stand toe to toe with the Pentium D 840 at around $530-ish. AMD's X2 4400+ and 4600+ models will face little direct competition from Intel, and Intel's low-end Pentium D 820 will face an asymmetric threat from AMD's single-core chips like the Athlon 64 3400+. These will be strange times, indeed.

AMD will not be abandoning high-performance, single-core processors once the X2 arrives, either. The Athlon 64 FX will get at least one more refresh this summer, aimed at gamers who want the highest possible performance in their single-threaded entertainment. Longer term, multi-core processors are no doubt the future, but AMD is moving more cautiously and conservatively into dual-core desktop parts than Intel.

One of the more intriguing questions about AMD's plans for the X2 has to do with its availability. AMD's official word on the matter now is that the Athlon 64 X2 will be "available in June," but when we visited AMD's Austin, Texas offices in March to talk about its dual-core product plans, we got an unexpected lesson in the anatomy of a "rolling product launch."

Here's the plan as they communicated it to us, stage by stage. The Athlon 64 X2 would first be announced at the time that dual-core Opterons were unveiled (and it was). Some time after that, reviews would happen (that's today). Next, there would be an official product launch. At that time, the first products would become available. (One could surmise that this day will come in June.) Initially, during the third quarter of the year, X2s would be sold primarily to OEMs and smaller system builders in Europe, as well as to system builders in the United States. After that, in the fourth quarter, AMD would turn its focus toward selling retail X2 processors in the U.S.

Obviously, initial availability will be sketchy, as it is now for Intel's Pentium Extreme Edition 840. Both AMD and Intel are rushing to get their dual-core products into the hands of reviewers well ahead of the time when the processors will be available in volume. We've seen such launch tactics applied innumerable times before, but rarely have we seen it mapped out in such exquisite detail. What we still don't know, however, is when A64 X2 processors will become available for eager PC enthusiasts to purchase via major online vendors like Newegg.com. Could be June; could be December. I suppose that depends less on what AMD has planned than on what AMD can manage to deliver. If so, only time will tell.