The IBM 305 RAMAC: The First Super Computer

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The IBM 305 RAMAC installed at US Army Red River Arsenal (now the Red River Army Depot) in Texas.

The first “super computer” containing a hard disk drive (HDD) stored 5 megabytes (MB) of data and weighed more than a ton. The IBM 305 RAMAC needed a room of at least 30 feet by 50 feet, and had to be moved with a forklift.

> RAMAC stands for Random Access Method of Accounting and Control

The 305 was introduced September 13, 1956 as the first commercial computer system that used a moving head HDD. The design of the system was inspired by the need for real-time accounting, and one of the first uses of the system type was at Chrysler’s MOPAR Division in 1957.

The 305 was also one of the last vacuum tube computers built by IBM, and it utilized an IBM 350 disk system that stored 5 million 8-bit characters across 50 disks that measured 24-inches in diameter each. Access arms would move up and down to select a disk, then in and out to locate a recording track. The average time to locate a specific record was 600 milliseconds (0.60 of a second).

IBM 350 Arm

The arms of the 350 moved up and down, and in and out, to locate specific records.

Additional components of the system included a card punch, card reader unit and printer. A manual inquiry station allowed for direct access to the records. The system was advertised as being able to store about 64,000 punched cards. Programming required the writing of machine language (instructions) or by using wire jumpers on a plugboard panel.

The 305 computer celebrated use during the 1960 Olympic Winter Games in Squaw Valley, California, where it used a punched card data collection system and a central printing facility.

In 1958 IBM enhanced the 305 to allow an additional 350 storage unit, doubling capacity to 10 MB. Unlike today, when businesses and consumers alike are easily tempted to purchase additional hard drives and cloud storage, IBM opted not to increase the storage capacity of the 305 any further because “they didn’t know how to sell a product with more storage.” (source: Currie Munce of Hitachi Global Storage Technologies)

In the late ’50s the cost to lease a 305 system using the 350 disk storage was $3,200 per month – more than $25,000 in 2010s dollars. The system also had a short lifespan. IBM had built more than 1,000 of them, but ended production of the 305 in 1961. By 1962, the entire system was obsolete.

To get a better idea of the complexity and operation of the IBM 305, take a look at this promotional video presented back then by IBM:

Last updated: Sep 13, 2012
Filed under: Retro Museum, Technology Tagged with: computers, technology