Hitachi has released a new family of SATA hard drives, and right at the top of the tree we have the 7K500 which uses five platters and ten read/write heads to achieve an enormous capacity of 500GB.

The rest of the 7K family is a bit of a mixed bunch so the 400GB version also uses five platters (i.e. 80GB per platter) while at the other extreme the tiny 80GB model uses a single platter. In the middle of the range there are two models which each boast a capacity of 250GB, which looks a bit odd.

The 7K250 uses three platters, which is around 80GB per platter, but the T7K250 reviewed here stands out because it is a twin-platter model, so each platter stores 125GB of data. The amount of data on each platter is significant because the tighter you pack it in, the less distance the read/write head has to move, and that increases hard drive performance.

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Another benefit of increased areal density is that the T7K250 uses fewer components than the 7K250 so it typically sells for £10 less and the twin-platter model has an operating noise level that is two decibels lower than the three-platter job. Be honest, you never thought that aluminium disks covered in magnetic media could be so interesting.

Specifications of the 7TK250 are fairly conventional by modern standards as it is a native SATA II design with 8MB of cache, a 7,200rpm spin speed and support for NCQ or Native Command Queuing.

NCQ speeds up the transfer of data between the hard drive and CPU, provided your motherboard or SATA controller card supports the technology. The idea is that the commands that are sent by the processor to the hard drive for data get queued up in a logical order to enable the drive to respond as quickly as possible. Think of it as though you organised your shopping list so you could go up and down the supermarket aisles more efficiently instead of tacking all over the place.

By far the least interesting part of the specification is the SATA300 interface, as this hard drive cannot transfer data at the implied rate of 30MB/second, but what it can do is offer fabulous performance. We tested the Hitachi drive back to back with the new Western Digital 150GB Raptor on an Intel D975XBX motherboard with a 3.46GHz Pentium Extreme Edition and 1GB of Samsung DDR2 memory.

Yes, the Raptor beat the Hitachi drive by about 25 percent in every test, but the overall effect was about seven percent as the hard drive is only one part of your PC. That makes the Raptor impressive but it costs £1.32 per gigabyte, while the Hitachi is cheap as chips at 30p per gigabyte.

The new 7TK250 is fast, cheap, quiet and cool. It represents superb value for money, and while 250GB isn't especially capacious these days, you could stick three of them in your PC for less than the cost of a single 500GB drive from a different manufacturer.