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Mobile ATA hard drives compared

We quantify the ultimate laptop upgrade
— 12:00 AM on April 27, 2006

SERIAL ATA MAY HAVE all but taken over on the desktop, but plain old ATA is still going strong in the mobile space. Only recently did Serial ATA support make its way into mobile core logic chipsets, and not all laptop manufacturers took advantage of that capability when it first became available. Many waited until second-generation Serial ATA chipsets, such as those in Intel's latest "Napa" Centrino platform, to transition laptop designs to SATA.

The slow pace of mobile SATA hard drive adoption has created a massive installed base of ATA-equipped laptops, many of which are ripe for a hard drive upgrade. Laptops generally come equipped with painfully slow drives with as little as 2 MB of cache and spindle speeds as slow as 4,200 RPM. These drives generally don't offer much in the way of capacity, either, with many topping out at only 30 or 40 GB. Fortunately, numerous alternatives exist, including drives with 8 MB of cache and spindle speeds as fast as 7,200 RPM. Greater capacities are available, as well, with most new mobile drives offering between 100 and 120 GB, and at least one leveraging perpendicular recording technology to crack the 160 GB mark.

To gain a better understanding of how the performance of today's latest and greatest 2.5" mobile ATA drives looks, we've gathered seven drives from the likes of Fujitsu, Hitachi, Seagate, and Western Digital. This mix of drives includes a little of everything, including a 160 GB perpendicular monster and a couple of 7,200-RPM speed demons. We've also thrown in a lowly 4,200 RPM drive that will serve as a handy reference point for anyone considering upgrading their laptop's hard drive. Join us as we subject this collection of drives to a punishing array of performance, noise level, and power consumption tests in search of the ultimate ATA laptop drive.

The 2.5" ATA form factor
For obvious reasons, laptops use a different hard drive form factor than your average desktop. Mobile drives—otherwise referred to as 2.5" drives—are significantly smaller than their desktop equivalents, measuring just 2.75" wide, 0.37" tall, and 3.96" long. 3.5" desktop drives, by comparison, measure 4" wide, 1.03" tall, and 5.79" long. As one might expect, desktop drives also weigh significantly more than the average laptop model. The average desktop drive weighs in at nearly half a kilogram, but the 2.5" mobile drives we'll be looking at today weigh closer to 100 grams.

A 2.5" ATA drive dwarfed by its 3.5" counterpart

Although petite proportions allow 2.5" drives to squeeze into ever-smaller laptop chassis, they also force mobile drives to use smaller, lower capacity platters than desktop drives. Drive manufacturers generally can't pack more than two platters per drive, either, while desktop drives can be found with up to five platters.

The use of fewer, smaller platters may restrict laptop drive capacity, but it also gives them less rotational weight. That allows drive motors to do less work, resulting in lower power consumption than your average desktop drive. Smaller laptop platters are also more resistant to physical shock—an important attribute considering laptops are generally subjected to more physical abuse than desktop PCs.

2.5" ATA (left) and Serial ATA (right) drives

One of the nicer things about 2.5" Serial ATA drives is the fact that they use the same power and data connectors as their desktop counterparts. Unfortunately, the 2.5" form factor's a little too svelte for that to work with ATA drives—standard IDE connectors alone are nearly as wide as the drives themselves. Since they can't accommodate traditional ATA data cables, 2.5" ATA drives are equipped with a 44-pin connector for both data and power. This connector works just fine for laptops, but those looking to run a 2.5" ATA drive in a desktop system will need an adapter.

A 2.5" ATA laptop drive adapter

The adapter translates those 44-pins to a standard IDE connector and four-pin Molex plug. Note that there are only two wires going to the power plug, though; one 5V line and one ground. Unlike desktop drives, which draw both 5V and 12V power, laptop drives run on just a single 5V line.

Perpendicular primer
While the bulk of today's hard drives use longitudinal recording technology to store data to disk, the desire for greater storage capacity has positioned perpendicular recording technology to succeed its parallel predecessor. Alas, we don't have the musical chops to explain perpendicular recording as well as Hitachi's infamous Get Perpendicular Flash animation, but our explanation won't get stuck in your head, either.

Longitudinal recording arranges bits horizontally in an orientation that's parallel to the surface of the disk, and that's worked pretty well for a while. However, as drive manufacturers try to squeeze a greater number of smaller bits onto each disk to increase storage capacity, they run into the Superparamagnetic effect, a phenomenon that occurs when ambient thermal energy causes extremely small particles to lose their magnetic orientation. Such a loss of magnetic orientation would flip a bit from 0 to 1, or vice versa, corrupting the integrity of data stored on a disk.

Bit orientations for longitudinal recording (above) and perpendicular recording (below)

The hard drive industry's solution to the Superparamagnetic effect is perpendicular recording, which, as its name implies, aligns bits vertically—perpendicular to the disk surface. This technique allows drive manufacturers to squeeze more bits onto a single disk platter, satiating our ever-growing need for greater storage capacity without resorting to smaller bits that could succumb to the Superparamagnetic effect. As an added bonus, perpendicular recording makes much more efficient use of a platter's available surface area, enabling areal densities that are expected to eclipse those offered by longitudinal recording by an order of magnitude.

Unfortunately, the first commercial perpendicular drives do not deliver these order-of-magnitude improvements in capacity. Thus far, Seagate's Momentus 5400.3 is the only perpendicular 2.5" mobile drive on the market, and its 80 GB platters are just 33% larger than the 60 GB platters used by the company's longitudinal drives. That's still a respectable capacity boost for a first-generation product, especially considering that even relatively modest gains in a platter's areal density can improve drive performance.