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MillimeterTest Drive: External Drive Connections, Part 1
Feb 11, 2008 12:00 PM, By Jan Ozer
Table 1. External drive connectors
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Technology Background
All of us know a little bit about external hard drives, but the big picture is sometimes tough to get your arms around. Hopefully, Table 1 will help. Let’s start at the top and USB 2.0.
Universal Serial Bus (USB) has two current relevant standards: USB 1.0, which runs at a maximum of 12Mbps, and USB 2.0, which maxes out at 480Mbps. Virtually all recently manufactured computers have USB 2.0 connectors, which makes them extremely convenient.
However, as we’ll learn in the next installment, actual relevant throughput for USB 2.0 is much, much less than FireWire, and it uses more of the host CPU to boot. For this reason, the USB connectors on your computer are best used for peripherals such as cameras, keyboards, mice, and printers, as well as casual storage such as that provided in USB thumb devices.
FireWire
As you probably know, FireWire was invented (in part) by Apple and formalized as IEEE 1394 by the Institute of Electrical and Electronics Engineers. There are currently two FireWire standards in general use: 1394a, or FireWire 400—which runs at a theoretical 400 Mbps—and FireWire 800, or 1394b—which runs at about 800Mbps.
Most notebooks have FireWire 400 connectors, but generally there’s only one connector per portable computer. If you’re actually capturing video on the notebook via that connector, it’s obviously impossible to capture to a FireWire 400 drive.
In contrast, while few notebooks come with a FireWire 800 connector (the MacBook Pro being one of them), as you can see from Table 2, an ExpressCard connector costs less than $50. This makes FireWire 800 ideal for connecting to an external hard drive while capturing video via the FireWire 400 port.
eSATA
eSATA is the relative new kid on the block for external hard drives, and it stands for External Serial Advanced Technology Attachment. As you probably know, most desktop computers started using SATA drives several years ago, and with a theoretical transfer rate of about 3GBps, SATA is clearly fast enough for DV and HDV editing. eSATA extends this speed to external drives—although the leash is short, because the maximum cable length is only 2m.
While the vast majority of SATA and eSATA devices that I’ve seen are full spec 3GBps SATA, you should know that the first generation of SATA interfaces, called SATA 150 or SATA 1, ran at 1.5GBps. If you decide to buy a SATA drive or adapter card, be sure that it’s SATA 3.0.
