USB & FireWire Drives

Dan Knight - 2001.05.21

Q. I need a bigger hard drive, but I'd like something I can also use on my friend's iMac. What should I buy?

A. You want an external hard drive. They come in pretty much any size imaginable today and use one of three connection options: SCSI, USB, and FireWire.

It used to be a lot easier. From the Mac Plus (1986) through the beige Power Mac G3 (1998), Macs had SCSI ports for external hard drives, scanners, CD-ROMs, etc. Even the PowerBooks had SCSI; many could even be connected to another Mac and used as an external SCSI drive. Although you can have Apple add SCSI to a Power Mac G4, no current Mac includes SCSI as a standard feature.

USB

That all changed with the iMac (1998), the first Mac in over a decade with no SCSI port. Your friend's iMac has a USB port, which we dubbed "okay for the low end" in 1998. USB is a slow protocol and tops out at 12 Mbps, less than one-third the speed of "slow-narrow" SCSI. Worse yet, Apple's implementation of USB only supports about half the throughput the spec allows.

USB on the Mac is fine for keyboards, mice, and game controllers. It's okay for scanners, floppies, and speakers. It's touch-and-go for burning CDs at 4x, which requires a constant 600 KBps (4.8 Mbps) data stream. It's slow for Zips and other removable media drives. And it's terribly slow compared with SCSI hard drives, so you only want to use USB for a hard drive as a last resort.

FireWire

All of today's Macs include FireWire, which offers much faster data transfer than USB - and also faster than all but the more recent, more expensive versions of SCSI. Compared with the 12 Mbps USB specification, the potential of FireWire to reach 400 Mbps is stunning; it's over 30x faster.

External Drive Options

If all you needed was more drive space, I'd recommend replacing the hard drive inside your computer, but you want something you can transport and use on your friend's iMac.

If your Mac supports FireWire, that's how you want to connect your external hard drive. Only consider a USB hard drive if it's your only option or an absolutely incredible bargain (in that case, you can probably put the drive in another case when your graduate to FireWire). In general, we recommend you plan ahead for FireWire so you won't be left behind with just USB.

I also suggest you consider building your own external drive with the enclosure and hard drive of your choice. If you're after a lot of storage on a budget, there are a lot of inexpensive, slower hard drives you can put in a case. If you want fast storage, there are faster, more expensive drives. (My current choice is the IBM Deskstar 75GXP, one of the fastest drives available and reasonably priced.)

You'll several types of cases to choose from depending on your hard drive - 2.5" drives designed for laptops fit in much smaller cases than 3.5" drives, but both the drives and cases tend to cost more. You'll also be able to pick a USB, FireWire, or combination enclosure.

Back in March, we reviewed a combination FireWire/USB enclosure from FireWire Depot. We found it easy to set up, reasonably fast with FireWire, and terribly slow with USB - pretty much what we expected. Reading from the disk was almost 13x faster with FireWire than USB; writing was over 10x faster. That's the reason we recommend USB as a last resort - it's simply slow.

On the other hand, a slow hard drive is better than no hard drive, so if USB is your only choice, you're stuck with it for now. That said, unless you're getting an absolutely incredible deal on a USB-only drive or enclosure, avoid USB-only drives and pick up a combination FireWire/USB drive. Even if all you can use today is USB, your next Mac will have FireWire - and your friend's may have it today.

Conversely, even if you have FireWire, if there's any chance you'll be using the drive with a USB-only Mac (including early iMacs, early iBooks, and the Lombard PowerBook G3), you might want to consider a combination drive instead of a FireWire-only one.

State of the Art

FireWire hard drives really use standard IDE/UltraATA hard drives inside a case with a bridge that adapts these drives to work with FireWire. Over the past few months we've begun a transition from first-generation FireWire bridges to the second generation, which is noticeably faster. (See our review of an enclosure using the Oxford 911 bridge for one example. Visit Bare Feats for a lot more on the subject.)

In testing the newer bridge, we found it 60-80% faster than the old one. If you're looking for the best performance, a fast UltraATA/66 or UltraATA/100 drive in an enclosure using a second-generation bridge is the way to go - it unleashes a lot more of the potential of FireWire.

If you're looking for the best value, you should be able to find some excellent bargains on enclosures using first-generation bridges along with a less costly IDE/UltraATA hard drive. (For instance, FireWire Depot was selling the SK 3.5 combination enclosure for $185 in February; it's down to $120 now.)

At this point, I don't know of any combination drives that use a second-generation bridge.

There are a lot of options out there: preassembled drives vs. choose your own enclosure and drive, 2.5" vs. 3.5" drives, cost vs. performance, and FireWire vs. USB vs. combination drives.