Seagate Momentus 5400.3 160GB Notebook HDD

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Feb 3, 2006 by Devon Cooke

Seagate Momentus 5400.3 ST9160821A
160GB, 5,400 RPM Notebook drive
Market Price

Perpendicular recording is here! Hard drive manufacturers have been talking about perpendicular recording for some time, but it has taken a while for the technology to reach the market. Now, Seagate has used the technology to produce a notebook drive with the highest capacity on the market.

What is perpendicular recording? Essentially, it's a way of packing bits on the disc more closely, thereby allowing higher areal density and greater overall disc capacity. Here is the core of the technology, from Seagate's white paper (in PDF format), Perpendicular Recording:

"To increase areal densities in longitudinal recording and boost overall storage capacity, the data bits must be shrunk and packed more closely together. However, if the bit becomes too small, the magnetic energy holding the bit in place may also become so small that thermal energy can cause it to demagnetize, a phenomenon known as superparamagnetism. To avoid superparamagnetism, disc media manufacturers have been increasing the coercivity (the field required to write a bit) of the media. However, the fields that can be applied are limited by the magnetic materials making up the write head.

"In perpendicular recording, the magnetization of the disc, instead of lying in the disc’s plane as it does in longitudinal recording, stands on end, perpendicular to the plane of the disc. The bits are then represented as regions of upward or downward directed magnetization. (In longitudinal recording, the bit magnetization lies in the plane of the disc and flips between pointing in the same and opposite directions of the head movement.) The media is deposited on a soft magnetic under-layer that functions as part of the write field return path and effectively produces an image of the recording head that doubles the recording field, enabling higher recording density than with longitudinal recording.

Image courtesy of Seagate.

"Seagate has demonstrated a recording areal density with perpendicular recording of 245 Gbpsi (Gigabits per square inch) with a data rate of 480 Mbits per second – more than double the 110 Gbpsi used in today’s highest areal density disc drives – and 500 Gbpsi, which will increase the capacity of today’s drives 5-fold, is possible with the new technology. At 500 Gbpsi, a 3.5-inch disc drive could store two terabytes of information, a 2.5-inch drive in a laptop could hold 500GB and a 1-inch drive, such as those in MP3 players, could store as much as 50GB of data."

(For all you techies, Hitachi has an incredibly geeky (and entertaining) flash animation with sound on the concept.)

SPCR has long recommended notebook drives as the quietest money can buy (short of solid state drives), but, until now, they were limited to 120 GB at most. Thanks to perpendicular recording, the Seagate Momentus 5400.3 boasts a capacity of 160 GB. That's still off the pace set by today's desktop drives but is nevertheless impressive — a 30% jump is nothing to sneeze at. As perpendicular recording matures, further gains are likely to be seen. Once the 2.5" form factor goes mainstream, perpendicular recording will help ensure that capacity is maintained.

SEAGATE MOMENTUS 5400.3 ST9160821A (quoted from Seagate's datasheet)

Nearly 50 percent more performance than systems with 4200-RPM drives

...but 4,200 RPM drives are quickly becoming obsolete.

4200-like battery consumption lets users work longer.

We'll see.

Robust design and high shock tolerance enable mobility in rugged notebook operating environments.

They all say this...

350 Gs of operating shock and 900 Gs of nonoperating shock make the drive ideal for notebook PCs and industrial applications.

More boasting about shock tolerance.

Initially, the 5400.3 will be available only with a Ultra-ATA interface — still the dominant interface for notebook drives. A SATA version of the drive will be available "later this year". This is disappointing news for desktop users, as SATA drives can be plugged directly into a desktop system without requiring a special adapter.

The 5400.3 follows in the footsteps of the 5400.2, which has a place on SPCR's Recommended list. Apart from the use of perpendicular recording, the two drives appear to be quite similar. The 5400.2 was a big improvement over the original Momentus, but model revisions are not always a good thing, especially for something like noise that gets little attention from manufacturers.

By now, it should be abundantly clear that the main improvement in the 5400.3 is the use of perpendicular recording, so it is worthwhile to examine what this means for the drive. One nice side effect of perpendicular recording is that it boosts areal density, which means that the data throughput should increase. The drive should take less time to access large, sequential chunks of data.

Seek latency, on the other hand, is not likely to be significantly affected, as latency is affected more by spindle speed and actuator technology than areal density. These performance differences show up in Seagate's specifications: Latency and seek time are identical to the 5400.2, while the internal transfer rate has increased.

For now, the 5400.3 is PATA only; SATA will probably come very soon.


The specifications below are specific to model that we examined. Capacity, cache size, platter number, interface, and even performance vary from model to model even within a single product line. Acoustics and power dissipation also vary depending on the number of platters in the drive; smaller capacity drives tend to have fewer platters, and tend to produce less noise and use less power.

Specifications: Seagate Momentus 5400.3 ST9160821A
160 GB
8 MB
Spindle Rotation Speed
5,400 RPM
Ultra ATA/100
5.6 ms
Average Seek
12.5 ms
Media Transfer Rate
44 Mbytes / second
102 g
Operating Temperature
0 - 60°C
Power Dissipation: Idle / Seek
2.0 / 2.0 W
Acoustics: Idle / Seek
2.3 / 2.9 Bels

For the most part, there's nothing out of the ordinary about the drive specs... except for the power dissipation, which is obviously incorrect. Both idle and read are rated for 2 watts, while (somehow) writes are supposed to drop to 1.8W. We'll have our own measurements for power dissipation later in this review.

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