2. 2.5" Vs. 3.5"

There is no significant technical difference between 2.5" notebook drives and 3.5" desktop drives other than their dimensions. While 3.5" drives have one to four platters, the more compact notebook drives usually have only one or two. That is necessary to keep the drives below the common drive height limit of 9.5 mm. The data density of notebook drives is very high today, with a maximum per-platter capacity of 50 GB.

When it comes to maximum data transfer rates, a 2.5" drive will never be able to compete with a 3.5". The reason is that the fastest transfers occur on the outside of the platter, and 3.5" platters have a larger circumference.

Taking a look at the interfaces, notebook drives have fallen behind desktop drives a little bit. While desktop hard drives are increasingly equipped with faster and easy-to-handle Serial ATA interfaces, notebook drives still use UltraATA/100.

This is not the fault of the drive manufacturers: we received some 2.5" drives with SATA interface last year. The issue here is the lack of available mobile platforms that support SATA, which has slowed the deployment of Serial ATA in the notebook sector. Intel's upcoming Sonoma platform, now scheduled for Q1/2005, will definitely change that. We expect to see the first 2.5" SATA hard drives in notebooks at that time.

Notebook drives will also be able to benefit from the advanced feature set in Serial ATA, such as hot plugging and command queuing. The latter has proven especially helpful in increasing a drive's efficiency.