Seagate has announced its thinnest ever hard drive, the 5mm thick Ultrathin HDD designed for the latest generation of slim laptops and tablets.

Every time it appears that the spinning hard drive is finally on its last legs and about to give way to solid state memory, manufacturers come up with another innovation to extend the technology's useful life.

What keeps the old-fashioned hard drive spinning these days is cost relative to storage capacity, something SSD designs still struggle to compete with.

The 2.5 inch 5,400rpm Laptop Ultrathin HDD chops 2mm from the company’s previous thinnest hard drive design of 7mm, equivalent to a 25 percent reduction and a new weight of 93 grams (3.3 ounces).

The company characterised this as being equivalent to the thickness of four credit cards. Despite its size, the SATA 6GB/s drive will be offered in capacities of 320GB and 500GB with no drop in performance.

The company sees the new drive as helping to make possible super-thin laptops, possibly thinner even than today's Ultrabooks.

“The new Seagate Laptop Ultrathin truly raises the bar, enabling us to finally create high-capacity, thin and light laptops that consumers crave at mass-market price points they can afford,” commented notebook head for Asus, S.Y. Shian.

“The drive’s capacity, coupled with its ultra-slim, lightweight footprint, empowers our engineers to think out of the box and create truly ground-breaking, innovative system designs.”

Costing $89 retail (£60), the drive is also being offered in a self-encrypting (SED) format in the 500GB version for enterprise use. The unit will also turn up in slim external USB drives at some point.

The company sees also the new drive as being used in tablet computers, a market that until now has relied on relatively low-capacity flash memory.

Seagate’s parallel push to keep hard drives relevant comes in the form of hybrid drives that combine spinning platters with some NAND flash capacity to speed booting up. Formerly known as Momentus XT drives, earlier this year these were rebranded ‘SSHD’.