160 GB In Your Notebook

Current 3.5" desktop drives offer capacities of up to 500 GB, with the 750 GB capacity point to be hit around the middle of this year. Compared to this, the 160 GB drives that are currently available for 2.5" drives seem almost small. Does this mean that 2.5" drives are falling behind?

This is not the case by any means, because there are some technical differences that need to be factored into this equation. First, 2.5" drives usually work with one or two magnetic platters, whereas 3.5" models can be equipped with up to five. Second, the platter diameter is much larger with 3.5" desktop hard drives, offering a larger total storage area. If you do an apples to apples comparison, looking at the areal density of storage, most 2.5" drives will actually do very well.

The small physical dimensions of 2.5" platters also have an impact on performance, as the highest absolute linear speed under the heads is lower with smaller discs. In addition to this general disadvantage, most 2.5" do not run at the 7,200 RPM speed that is common in the 3.5" space; they spin at only 5,400 or even 4,200 RPM.

For many years most drives were the slower 4,200 RPM speed. Yet there is a wind of change in the notebook hard drive space, because seven of the eight new drives we received for review spin at 5,400 RPM with only a single one at 4,200 RPM. The interface question remains pretty balanced: Four drives use UltraATA/100, while the remaining four are based on Serial ATA/150.