Thread: Early Disk Drives

The very first disk drives were of course experiments. Researchers, particularly those at IBM, were working with a number of different technologies and concepts to develop a disk drive that would be feasible for commercial development. In fact, the very first drives were not "disk drives" at all-they used rotating cylindrical drums, upon which the magnetic patterns of data were stored. The drums were large and hard to work with. The earliest "true" hard disks had the heads of the hard disk in contact with the surface of the disk. This was done to allow the low-sensitivity electronics of the day to be able to better read the magnetic fields on the surface of the disk. Unfortunately, manufacturing techniques were not nearly as sophisticated as they are now, and it was not possible to get the disk's surface as smooth as would be necessary to allow the head to slide smoothly over the surface of the disk at high speed while in contact with it.


Over time the heads would wear' out, or wear out the magnetic coating on the surface of the disk. The key technological breakthrough that enabled the creation of the modem hard disk came in the 1950s. IBM engineers realized that with the proper design. the heads could be suspended above the surface of the disk and read the bits as they passed underneath. With this critical discovery that contact with the surface of the disk was not necessary, the basis for the modem hard disk was born.
The very first production of hard disk was the IBM 305 RAMAC (Random Access Method of Accounting and Contro!), introduced on September 1956. This hard disk could store 5 million characters.



Over the succeeding years, the technology improved im:rementally. In 1962, IBM introduced the model 1301 Advanced Disk File. The key advance of this disk drive was the creation of heads that floated above the surface of the disk. In 1973, IBM introduced the model 3340 disk drive, which is commonly considered to be the father of the modem hard disk. This unit had two separate spindles, one permanent and the other removable, each with a capacity of 30 MB. For this reason the disk was sometimes referred to as the "30-30". This name led to its being nicknamed the "Winchester" disk drive, after the famous "30-30" Winchester rifle. Modem hard disks today still use many concepts first introduced in this early drive, and for this reason are sometimes still called "Winchester" drives. The first hard disk drive designed in the 5.25" form factor used in the first PCs was the Seagate ST-506. It featured four heads and a 5 MB capacity. IBM bypassed the ST-506 and chose the ST-412-a 10 MB disk in the same form factor-for the IBM PC/XT.