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SATA 6Gbit/sec.: Does it double your SATA speed?

We pit two new SATA 6Gbit/sec. hard drives against older peers to see how much faster they really are.

By Bill O'Brien
April 15, 2010 06:00 AM ET

Computerworld - Those of us in the business of keeping an eye on new technologies wonder why the buzz about SATA 6Gbit/sec. (a.k.a. Serial ATA Revision 3) hasn't been louder than it is.

SATA 6Gbit/sec. is the next-generation SATA specification and will double the speed of the current SATA standard (which is 3Gbit/sec.). The technology was first demonstrated by Seagate and AMD in March 2009, and is finally coming to market. So why haven't we heard more about it?

WD Caviar Black
WD Caviar Black

Even some hard drive manufacturers are being coy about the new specification. For example, a Western Digital representative, when asked about the company's 1TB SATA 6Gbit/sec. Caviar Black, said that Western Digital had not made a major announcement because SATA Revision 3 just represents an interface change.

Just an interface change? Yes, technically that's correct. SATA Revision 3's speed rating -- like all of the other SATA and Parallel ATA (PATA) ratings -- is actually a measurement of the speed at which data travels from the hard disk's onboard cache to the interface on your PC. It really has nothing to do with the speed of the drive itself.

So is this new SATA technology irrelevant? Not at all. One only has to imagine its use with drives having higher rotational speeds than the current 7,200 rpm (they get to the data more quickly); drives with larger onboard cache (that will hold more data in readiness for the interface to absorb); and even SSDs where none of the offsets of mechanical hard disks exist. It could significantly improve performance in all of those scenarios.

Even with the current crop of drives -- especially with those that have increased cache values of 64MB and up -- SATA 6Gbit/sec. should add some increase in burst speed and sequential reads or writes to contiguous disk sectors. These procedures maximize the continuous streaming of data that a faster interface speed can take advantage of.

Barracuda XP
Seagate Barracuda XT

To see how much of an advantage this new technology will add, I tested two new SATA 6Gbit/sec. hard drives: The 1TB Western Digital WD Caviar Black ($120) and Seagate's 2TB Barracuda XT desktop hard drive ($260).

Like the new USB 3.0 specification, SATA 6Gbit/sec. is a whole new technology. If you want to use a SATA 6Gbit/sec. hard drive, you'll need a motherboard that provides a SATA 6Gbit/sec. interface (which, if you're building your own system, will cost somewhere between $140 and $240, depending on the type of features you want). If you don't want to replace your motherboard, you can add a SATA 6Gbit/sec. plug-in card, such as the Asus U3S6, to an existing motherboard. Be aware, however, that these cards usually require an x4 PCIe slot and you might be hard-pressed to find an available one in your current PC inventory.

To take full advantage of the technology, you'll also want a system with at least an Intel Core i5 processor (to make use of Intel's SATA 6Gbit/sec.-supporting X55 chip set), at least 4GB of memory and a decent graphics card.

Using SATA 6Gbit/sec. with a SATA 3Gbit/sec. motherboard

If you're thinking about buying either drive and plugging it into a SATA 3Gbit/sec. motherboard, that's not something I'd recommend. While both of the current SATA 6Gbit/sec. offerings are backward-compatible with SATA 3Gbit/sec., they lose all their advantages in the process.

The Barracuda XT, for example, could only muster 180.1MB/sec. burst speed when it was connected to an older port, but it hit 296.6MB/sec. when attached to its native interface. Write speed was also down somewhat -- the Barracuda XT needed 20 seconds more to complete the write test with the slower interface. (The read speeds with the two interfaces were nearly identical, however.)

Western Digital's Caviar Black suffered a similar fate: Its burst speed dropped from 320.7MB/sec. (using its native interface) to 206.0MB/sec. Its average read time took a small hit, from 112.4MB/sec. to 108.9MB/sec., and its performance in the read test went from 4 minutes, 32 seconds to 5 minutes, 9 seconds. (In this case, write speeds were pretty much the same.)

In fact, all of the 3Gbit/sec. drives were faster reading and writing my data packet than either of the SATA 6Gbit/sec. drives attached to a 3Gbit/sec. interface. That makes a SATA 6Gbit/sec. hard drive a poor choice for either interface type compared to what's already available for data writing or retrieval involving large blocks of information.

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