Toshiba has expanded its line of 1.8-inch hard-disk drives for laptops, netbooks and other mobile PCs.

The latest offerings include a new series of drives with disk speeds of 5,400 revolutions per minute. The new line, called the MKxx33GSG series, comes in storage capacities of 160 GB, 250 GB, and 320 GB. Other specifications include a 16 MB cache buffer and disk-transfer rates of up to 830 Mb per second.

In addition to the MKxx33GSG series, Toshiba unveiled a more power-efficient and slimmer 4,200 RPM model. The single-platter MK1235GSL has a storage capacity of 120 GB. The HDD is 0.2 of an inch thick and is built for netbooks and other mobile PCs that trade storage size for longer battery life. Other specifications include an 8 MB cache buffer and disk-transfer rates of up to 533 Mbps.

Toshiba markets its line of 1.8-inch HDDs as more rugged and power-efficient than 2.5-inch drives used in many mobile PCs. The company claims its MKxx33GSG series uses 42% less power during seek operations than 5,400 RPM 2.5-inch drives.

In addition, the smaller drives can withstand 1,500 Gs of non-operational shock and 500 Gs of operational shock, which is 50% and 25%, respectively, more durable than the larger HDDS, according to Toshiba.

The MKxx33GSG series is scheduled to enter mass production in early December. The MK1235GSL model is shipping in volume production.

HDDs in mobile PCs are expected to eventually giving way to solid-state drives, which are more durable, faster and use less power. However, SSDs today are significantly more expensive and cannot match HDDs in storage capacity. Therefore the transition could take years, analysts say.

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