When Western Digital introduced its GreenPower line with the terabyte Caviar GP last year, we wished aloud that the drive's new 250GB platters would make their way into a performance-oriented model. The GP wasn't even particularly slow—in fact, it was the fastest terabyte drive at the time. But by dialing back the GreenPower's spindle speed to close to 5,400RPM in a bid to improve energy efficiency, WD effectively left some performance on the table. We've been waiting to get that performance back ever since.

Unfortunately, it seems Western Digital had no plans to sate our desire for a terabyte Caviar with 250GB platters spinning at a full 7,200RPM. Instead, the company has almost done one better by launching a new batch of 7,200-RPM Caviars that pack an impressive 320GB per platter. These new drives are only available in capacities up to 640GB, so they won't challenge for the terabyte crown. With prices hovering around $130 for the 640GB model, however, this latest crop of Caviar nails the cost-per-gigabyte sweet spot that most enthusiasts covet.

The question, of course, is how this new Caviar SE16 640GB measures up. Can Western Digital's new Caviar models match up with Samsung's best-in-class SpinPoint F1? And with only two platters, does this new SE16's noise levels and power consumption compete with energy-efficient drives like the Caviar GP? Keep reading to find out.

Mo' areal density
320GB platters are easily the most interesting component of the Caviar SE16 640GB; they allow Western Digital to hit the 640GB mark using only two platters, lowering the odds of a catastrophic head crash simply by reducing the number of platters a head could crash into. Using fewer platters also reduces the rotational load on the drive motor, which should allow it to run quieter while consuming less power than drives with more platters.

By far the biggest benefit of the SE16's new platters comes in the form of performance potential. The 320GB platters boast an areal density 28% higher than that of Western Digital's 250GB discs, giving the drive head access to substantially more data over shorter physical distances. Increases in areal density can dramatically improve sequential transfer rates, although it is worth noting that WD's 320GB platters don't have the highest areal density on the market. That honor belongs to the 334GB platters in Samsung's SpinPoint F1.

The new Caviar SE16 falls a little short of the F1 on the overall capacity front, as well. Samsung offers the SpinPoint in a three-platter configuration that serves up a cool terabyte of storage, but Western Digital is only packing up to two platters in its latest SE16s, limiting their maximum capacity to 640GB. We've seen three-platter Caviars before, and it should be possible for WD to put together a 960GB drive with its new 320GB media. However, the company hasn't announced plans for such a product. A single-platter 320GB Caviar SE16 model is available if you don't need quite as much capacity, though.

Interestingly, Western Digital is sticking with a 16MB cache for its new Caviars. Hitachi, Seagate, and Samsung have all put 32MB of memory into their latest drives, leaving the Caviar looking a little light. However, WD says it has done extensive performance profiling that shows little benefit to jumping from 16 to 32MB of cache.

Like other recent Caviar models, the new 640GB SE16 features an IntelliSeek actuator mechanism that only moves the drive head as fast as necessary (rather than as fast as possible) to get it into position for the next data point. This just-in-time delivery scheme is designed to reduce seek power consumption, noise, and vibration, and Western Digital says it has no impact on actual drive performance.

To further combat vibration, the Caviar SE16 is equipped with a SecurePark mechanism that moves the head completely off the disc when the drive is powered down, as well as during spin-up and spin-down. This mechanism ensures the drive head is only flying over the platter when needed and that it never actually rests on the surface of the platter.

Caviar SE16 hard drives are covered by a three-year warranty that matches the industry standard for desktop drives. Three years of coverage should be enough for most folks, especially considering how quickly capacities have ramped over the last few years. However, enterprise-class products like Western Digital's Caviar RE2 line enjoy five years of warranty coverage. Seagate also offers a five-year warranty for all its internal hard drive products, including desktop Barracudas that compete directly with the SE16.