RAMAC

(Random Access Method of Accounting and Control) The first hard disk computer, introduced by IBM in 1956. All 50 of its 24" platters together held a total of five million 8-bit alphanumeric characters (5MB). Weighing more than a ton, RAMAC was half computer, half tabulator, and more than a thousand units were built until production ceased in 1961. The RAMAC had a drum memory for program storage, but its I/O was wired by plugboard. The machine was a major breakthrough as all prior computer storage used magnetic tape.

RAMAC leased for USD $38,400 per year, equivalent to roughly $300,000 in 2019 dollars. About a third of the cost was RAMAC's "huge" disk system. However, 60 years later, that same amount of storage cost less than one thousandth of one cent on a multi-terabyte hard drive. See tabulator.

The RAMAC, 1956

At 2,000 magnetic bits per square inch, IBM's RAMAC was an amazing technology in the 1950s. Each 24" platter held a whopping 100,000 characters (no bytes then) for a total of five million characters. (Images courtesy of IBM.)

The RAMAC, 1956

At 2,000 magnetic bits per square inch, IBM's RAMAC was an amazing technology in the 1950s. Each 24" platter held a whopping 100,000 characters (no bytes then) for a total of five million characters. (Images courtesy of IBM.)

RAMAC Resurrected

In 1994, IBM reinstated the RAMAC name for its hard disk arrays. In 38 years, areal density vaulted from 2,000 to 259,500,000 bits per square inch, and access time decreased from 600 milliseconds to 9.5. (Image courtesy of IBM.)

Would They Have Believed It?

A sale at Staples for 25,000 times as much random access storage cost 1/1000th of one month's rent of the RAMAC in 2019 dollars.