USB 2.0 is the most popular connection technology for external devices, with FireWire (either 400 or 800) a close second. However, if you really want extreme speed, eSATA is the way to go, as Seagate Technologies' new FreeAgent XTreme drive proves.

I tested the 640GB model (ST306404FPA2E3-RK, US$179.99). The drive includes the unit itself, a one-piece power supply, a quick start guide (basically an illustrated "what to plug in where" sheet), plus one USB 2.0 and one Firewire 400 cable. No eSATA cable is provided. Installation is simple: plug it in, connect the appropriate cable, turn on the drive, and you're ready to go.

The drive is compatible with Windows Vista SP1 as well as Windows XP SP2, SP3.

Going to extremes

The drive rotates at 7200rpm and was preformatted in NTFS. Windows XP SP3 reported 596.2GB of space available. I tested the drive using HD Tach 3.0 from Simpli Software Inc. Using its thorough Long Bench test (which uses 32KB blocks for reads and writes across the entire drive), the drive registered a burst speed of 32 MB/sec., an average read speed of 30.3 MB/sec., and CPU utilization of 23% when connected to the USB port, roughly on par with the Buffalo DriveStation Combo 4 I reviewed in July -- a 1TB external drive with the same three connectors plus FireWire 800.

Using version 2.55 of the HD Tune benchmark test, the drive recorded an average transfer rate of 29.8 MB/sec., an average access time of 15.2 milliseconds, and a burst rate of 24.5 MB/sec., using 13.1% of the CPU.

Performance improved when I connected the drive to the FireWire 400 port. HD Tach reported a higher burst speed (42.1 MB/sec.) and a 32% improvement in read speed (to 40.0 MB/sec.), using just 1% of the CPU. HD Tune results showed similar improvement: an average transfer rate of 38.0 MB/sec., average access time of 15.0 milliseconds, and a burst rate of 35.3 MB/sec. using just 1% of the CPU.

eSATA is still not a standard feature of most PCs, and it wasn't built in to the motherboard on my test machine, so to get the fastest possible speed, I installed a Promise SATA300 TX4302 card ($90). The card connected to my Dell system using a standard PCI slot and came with two internal and two external 3 GB/sec. ports, and (thankfully) all the cables needed to connect up to four drives. Only one external port was used during testing.

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