Seagate FreeAgent Go 1TB and 640GB portable USB drives

Storage
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TESTING

Since this is the first time that we've reviewed any external drives, we don't have an established testing methodology. We decided to fall back on our standard hard drive testing methodology, which is meant for internal hard drives. Most of the acoustics tests are done in our own 10~11 dBA anechoic chamber. Noise is our number one priority, and great effort is taken to ensure it is comprehensively measured and described. Performance is covered only lightly, for reasons discussed in detail in the methodology article.

Two forms of hard drive noise are measured:

  1. Airborne acoustics
  2. Vibration-induced noise.

These two types of noise impact the subjective perception of hard drive noise differently depending on how and where the drive is mounted.

Both forms of noise are evaluated objectively and subjectively. Airborne acoustics are measured in our anechoic chamber using a lab reference microphone and computer audio measurement system. Measurements are taken at a distance of one meter from the top of the drive using an A-weighted filter. Vibration noise is rated on a scale of 1-10 by comparing against our standard reference drives.

Summary of primary HDD testing tools:

A final caveat: As with most reviews, our comments are relevant to the samples we tested. Your sample may not be identical. There are always some sample variances, and manufacturers also make changes without telling everyone.

Ambient conditions in the anechoic chamber at time of testing were 10.5 dBA and 22°C. In the normal rooms, the ambient ranged, 18~28 dBA, and 20~26°C.

PERFORMANCE

The performance of USB 2.0 external drives is limited mostly by the USB interface, and the characteristics of the drive within. The USB controller chip in the motherboard can also play a part, as well as the operating system and the hard drive on the PC. Both of the PCs used for testing were equipped with extremely high performance drives — the Windows XP PC has a WD VelociRaptor 10,000 RPM drive while the Windows 7 PC is equipped with an Intel X25-80GB solid state drive. This ensures that the limitation of performance is the external drive being tested, not the PC's drive.

With these FreeAgent Go drives, the performance was so similar that they might as well have been the same drive. This is not surprising, considering that they both spin at 5400 RPM, with aerial density around the same 320gb/platter range. Results from both drives are presented as if they were one.


FreeAgent Go 1TB drive on Windows XP Athlon X2 64 PC system. The 640GB drive produced virtually identical results on this system.


FreeAgent Go 640GB drive on Windows 7 Athlon II X2 PC system virtually identical performance. The 1TB drive produced virtually identical results on this system.


Seagate FreeAgent Go - File Transfer Tests
Function
640GB
1TB
Read/write 8.3 GB file on Windows XP system
4:46 / 4:55
4:37 / 4:48
Read/write 8.3 GB file on Windows 7 system
4:36 / 4:50
4:31 / 4:40
Read/write 1.8 GB file on Windows XP system
1:00 / 1:06
0:58 / 1:04
Read/write 1.8 GB file on Windows 7 system
0:56 / 1:01
0:55 / 1:02

The performance results above are about the best that can be expected with these devices. Care was taken to ensure that there were no other loads on the USB ports or on the main OS drive. (The 19.7% CPU load seen in the Window 7 HD Tune Pro result is an anomaly. Typical CPU usage is typically 2-4%.) In general, the FreeAgent Go drives are fast enough for routine use.

POWER DRAW

We know from testing many 2.5" drives in the past that they typically idle at 1W or less, and peak at about 2.5W during write/read operation. A reading of the USB 2.0 and 3.0 Specifications indicates that maximum rated current for each port is 500mA and 900mA, respectively, at 5V. This translates to 2.5W per USB 2.0 port. The current is supplied by the 5V standby line in a PC, usually rated for at least 2.5A. However, the specs appear to be recommended ratings for external USB devices. The Intel ATX12V Power Supply Design guide v2.2 mentions, for example, that on wakeup, an external USB device may cause a "peak currents as high as 3.5A lasting no more than 3 seconds", referring probably to spin-up of an external hard drive. It's not clear whether there is current limiting in the port circuitry; non-compliant devices might be able to draw more than 2.5W, with potential higher than normal long-term stress on the USB circuitry in the PC.

In the recent past, some external 2.5" drives were supplied with a USB cable that had two plugs on the PC side to ensure enough current could be drawn safely. As you know from photos above, the cables for these FreeAgent Go drives have just one port per end. Still, the drive in our FreeAgent Go 1TB is rated for 0.75A at +5V or 3.75W, probably the maximum at spin-up. (See the last page for photos and details.)

It's not easy to test the power draw through a USB connection. About the best we could come up with was to monitor the power draw of a laptop while running these USB 2.0 external drives from it. The battery from the notebook was removed altogether to prevent any extra power going to charge the battery.

AC Power Draw
AC Power
idle
read/write
Laptop only
11W
15W
with FreeAgent Go 640GB
13.6W
20W
with FreeAgent Go 1TB
13.7W
21W

The result aren't exactly definitive, but it appears that the 640GB and 1TB draw about the same power from the USB line when idle. The 2.6~2.7W AC additional at idle seems inordinately high given that the drives actually pull no more than 1W DC, even if you includes the power lost through the AC/DC conversion of the laptop. During read/write, the power jumps to around 5~6W AC maximum, which again seems too high. In any case, running these (or any) USB-powered drives off a laptop will have some impact on overall run time on battery; many low power laptops draw just 10~15W AC in normal use, so even the minimal additional load of a USB drive in idle could result in a 10~20% reduction in untethered run time.



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