UNIVAC III

The UNIVAC III, designed as an improved transistorized replacement for the vacuum tube UNIVAC I and UNIVAC II computers, was introduced in June 1962. It was designed to be compatible for all data formats. However the word size and instruction set were completely different; this presented significant difficulty as all programs had to be rewritten, so many customers switched to different vendors instead of upgrading existing UNIVACs.

The system was engineered to use as little core memory as possible, as it was a very expensive item. They used a memory system which had 25 bits width, and could be configured with from 8,192 words to 32,768 words of memory. Memory was built in stacks of 29 planes of 4,096 cores: 25 for the data word, 2 for "modulo-3 check" bits, and 2 for spares. Each memory cabinet held up to four stacks (16,384 words).

It supported the following data formats:
*25 bit signed binary numbers
*excess-3 binary coded decimal with 4 bits per digit, allowing 6 digit signed decimal numbers
*alphanumerics with 6 bits per character, allowing 4 character signed alphanumeric values

Sperry Rand began shipment in June 1962 and produced 96 UNIVAC III systems.

The operating systems(s) which were developed for the UNIVAC III's were called CHIEF, and BOSS. The largest number of UNIVAC III systems were equipped with tape drives, so tapes contained images of the system data at the head of any tape, followed by data. The OS could handle jobs at this time, so some tapes had data relating to job control, and others had data. UNIVAC III systems could have up to 32 tape drives.

Some systems were equipped at a later time with FASTRAND drum, as the original design with only tape drives was found to be a drawback.

ee also

*List of UNIVAC products
*History of computing hardware

External links

* [http://ed-thelen.org/comp-hist/BRL61-u4.html#UNIVAC-III UNIVAC III Data Processing System] "A Third Survey of Domestic Electronic Digital Computing Systems" Report No. 1115, March 1961 by Martin H. Weik, published by Ballistic Research Laboratories, Aberdeen Proving Ground, Maryland (at that time the computer was not yet available, 25 systems were on order and the time required for delivery was 18 months after placing the order)
* [http://www.cc.gatech.edu/~randy/folklore/v2n1.html The UNIVAC III Computer]
* [http://jwstephens.com/univac3/page_01.htm UNIVAC III Photos]
* [http://stephens.st/univac3/Univac3Serials.html UNIVAC III installations (serial numbers given where known)]
* [http://www.bitsavers.org/pdf/univac/univac3/ UNIVAC III Documentation] (PDF) on bitsavers.org