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 and SP3.

Going to extremes

The drive rotates at 7200 rpm 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.

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 32MB/sec., an average read speed of 30.3MB/sec., and CPU utilization of 23 percent 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 29.8MB/sec., an average access time of 15.2 milliseconds, and a burst rate of 24.5MB/sec., using 13.1 percent of the CPU.

Performance improved when I connected the drive to the FireWire 400 port. HD Tach reported a higher burst speed (42.1MB/sec.) and a 32 percent improvement in read speed (to 40.0MB/sec.), using just 1 percent of the CPU. HD Tune results showed similar improvement: an average transfer rate of 38.0MB/sec., average access time of 15.0 milliseconds, and a burst rate of 35.3MB/sec. using just 1 percent 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 (US$90). The card connected to my Dell system using a standard PCI slot and came with two internal and two external 3GB/sec. ports, and (thankfully) all the cables needed to connect up to four drives. Only one external port was used during testing.

Using this configuration, HD Tach reported a burst speed of 100.3MB/sec. and a read speed more than double that of the FireWire 400 test (81.6MB/sec.), with just 2 percent of the CPU used. The HD Tune test was equally strong: an average transfer rate of 76.8MB/sec., average access time of 15.0 milliseconds, and a burst rate of 61.6MB/sec. using just 4.4 percent of the CPU.

To compare its speed with another recently released external drive, I retested the Buffalo DriveStation using the same Promise card. Results were only slightly slower for HD Tach, which reported 96.7MB/sec. burst speed, an average read speed of 71.4MB/sec., and CPU utilization of 4 percent. With HD Tune, the results were roughly equal: average transfer rate was 75MB/sec., average access time was 14.0 milliseconds, and CPU use was 5.6 percent.