Engineers at Toshiba have demonstrated a working prototype of a hard disk drive that crams in 50 percent more data than previous models and paves the way for higher capacity drives.

The drive, unveiled last week at the company's research and development centre in the Tokyo suburb of Ome, manages to pack 52Gb (gigabits) of data on to one square inch of magnetic recording space. This is the disk's areal density.

That's a big jump on the company's current highest capacity commercial drive, a 2.5in, one-platter 20GB model that has an areal density of 35.1Gbpsi (gigabits per square inch). In contrast, the areal density achieved with the prototype drive translates into a capacity of 30GB per 2.5in drive platter.

Platters are the circular discs coated with a magnetic material on which data is recorded. Hard drives use multiple platters to gain their total disk space.

Toshiba says it expects the technology won't find its way into commercial products until later this year, or perhaps even as late as sometime next year.

Meanwhile researchers are already concentrating on doubling drive capacity to 100Gbpsi before the end of 2003.

Toshiba is in a race with other leading hard disk drive makers to increase areal density in order to produce higher capacity hard disk drives. This is especially important for drive platters with diameters of 2.5in and below because their smaller size means there is less physical space for data.

IBM's latest 2.5in drive, the Travelstar 40GN, has an areal density of 34Gbpsi and capacity of 20GB per platter, while Fujitsu's MHR series 2.5in drives, introduced in October 2001, boasted a 36.1Gbpsi areal density but still only 20GB per platter.

Toshiba's development of a new type of AV-HDD (Audio-Visual hard disk drive) for use in consumer electronics products is almost complete, and the drive is expected to be on the market before the end of March.

Unlike drives for PC use, standard AV-HDDs impose time limits on the speed with which information can be read off the drive so as to ensure a steady video or audio stream. But one of the side-effects of this is increased noise, said Yutaka Arakawa, a specialist in Toshiba's hard disk drive development department.

Toshiba's new drive, a 40GB 2.5in model, cuts most of the noise usually associated with AV-HDDs but retains the time limit on read operations to ensure a smooth stream of data, he said. Also under development is a shock-resistant hard disk drive for use on the move.