To give its 10K-RPM Serial ATA drives more widespread appeal, Western Digital upped the Raptor's capacity to 74GB for the WD740GD model, but didn't stop there. The new Raptor's internals have also been tweaked to give the drive faster seek times and transfer rates, lower noise levels, and support for command queuing. How does this latest Raptor fare against its Serial ATA and SCSI-based competition? Let's find out.
Before we look at the performance of this latest Raptor, let's see how the WD740GD's specs compares with those of its predecessor.
|Maximum internal transfer rate||816Mbits/sec|
|Maximum external transfer rate||150MB/sec|
|Average sustained transfer rate||72MB/s||55MB/s|
|Average seek time (read)||4.5ms||5.2ms|
|Average seek time (write)||5.9ms|
|Average rotational latency||2.99ms|
|Serial ATA interface||Marvell 88i8030C bridge||Marvell 88i8030 bridge|
|Warranty length||Five years|
In many ways, the WD740GD is identical to the WD360GD. Both drives feature 10,000RPM spindle speeds, 8MB of cache, 37GB platters, and five-year warranties. However, the WD740GD has a quicker read seek time and faster average sustained transfer rate than its little brother. The WD740GD also uses fluid dynamic bearings, which should make it quieter than the WD360GD.
Despite its somewhat menacing specs, the WD740GD's appearance doesn't exactly exude speed. Then again, hard drives tend to look alike.
The easiest way to distinguish the WD740GD from a "parallel" ATA hard drive is to look at its interface ports. Though the drive features a standard four-pin Molex connector, it's also packing Serial ATA data and power plugs. You can use either of the drive's power plugs, though I prefer the four-pin Molex plug since it fits a little more snugly than the Serial ATA power connector.
Although the Serial ATA spec does away with master/slave relationships, the WD740GD still has a jumper block. Rather than controlling the drive's master or slave status, the jumper block is used to enable a special power-saving mode that boots the drive in a standby state. Western Digital recommends the drive's standard power mode for most users, though.
Thus far, everything about the WD740GD suggests that it will offer better performance than its predecessor right out of the box. As if that weren't enough, the WD740GD should also get a performance boost when Serial ATA controllers support the drive's Tagged Command Queuing (TCQ) feature. The original Raptor lacks TCQ support, which allows the WD740GD to re-order outstanding requests with efficiency in mind. Unfortunately, Serial ATA controller cards with command queuing support have yet to hit the market.
The WD740GD's TCQ support should help the drive compete with SCSI gear, which already supports command queuing. The performance benefits of TCQ should be especially apparent in multi-user benchmarks like IOMeter, where the original Raptor doesn't scale as well under increasing loads as 10K-RPM SCSI drives. We'll be sure to revisit the WD740GD when Serial ATA controllers that support command queuing become available.