hard drive history

beginings: mfm drives of the 1980s

Four Seagate greats

Photo: Red Hill.

Seagate ST-225

Old reliable. Allowing for market growth over the years, the ST-225 was undoubtedly the best-selling hard drive of all time, as astonishing in its own way as the Z-80 was in its.

The ST-225 was the single most common 20MB drive, and certainly the longest lived. It set the pattern for what would become the traditional, almost the inevitable, entry-level Seagate: a surprisingly low price, ugly styling, modest but reasonable performance, and outstanding reliability.

Incredibly, we would still see ST-225s once in a blue moon right up to the end of the century, fifteen or twenty years old by then, and going just as strong as ever.

The drives illustrated above are four of the Seagate greats. At left, the 20MB ST-225; at top right, the full-height 10MB ST-412, bottom, the ubiquitous Medalist 545; and centre, the tiny 19mm high racehorse Decathlon 850. All four would feature high on any list of all-time great hard drives.

Together with the even older 5MB ST-506, the ST-412 pioneered the ST-412/506 (MFM) interface. The ST-225 was the drive that, more than any other, made it reliable and affordable.

Data rate5 Mbit/secSpin rate3600 RPM
Seek time65msActuatorStepper
Platter capacity10.5MBInterfaceMFM
AT drive type2Form5.25" half-height
ST-22521.4MB4 heads1984
ST-225 or ST225 - the definitive answer

A note about confusing model names.

Seagate now refers to old drives like the ST-225 as "ST225" without the hyphen. Seagate started using model numbers sans hyphen in about 1991 or '92 — the first Seagate 40MB IDE was the ST-157 but the last one was the ST351.

But watchout! Seagate publications continued sometimes adding and sometimes not adding a hyphen after the "ST" for more than a decade, so if you are searching, key in both forms. For these pages, I take the form written on the drive itself as the final authority.)