The UNIVAC III, designed as improvement to the UNIVAC I and UNIVAC II, 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. UNIVAC I central complex, containing the central processor and mercury memory. ... The American company UNIVAC began as the business computer division of Remington Rand formed by the purchase of the Eckert-Mauchly Computer Corporation (EMCC) in 1950. ... 1962 (MCMLXII) was a common year starting on Monday (the link is to a full 1962 calendar). ...

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

Instructions were 25 bits long. Excess-3 binary coded decimal (XS-3) is a numeral system used in some old computers. ... Binary-coded decimal (BCD) is a numeral system used in computing and in electronics systems. ...

The CPU had 4 accumulators, a 4 bit field (ar) allowed selection of any combination of the accumulators for operations on data from 1 to 4 words in length. For backward compatibility with the UNIVAC I and UNIVAC II data; two accumulators were needed to store a 12-digit decimal number and three accumulators were needed to store a 12-character alphanumeric value. When accumulators were combined in an instruction, the sign bit of the Most Significant Accumulator was used and the others ignored.

The CPU had 15 index registers, a 4 bit field (x) allowed selection of one index register as the base register. Operand addresses were determined by adding the contents of the selected base register and the 10 bit displacement field (m). Instructions that modified or stored index registers used a 4 bit field (xo) to select that index register.

Indirect addressing or field selection was selected if the 1 bit field (i/a) was set. Both indirect addressing and a base register could be selected in the indirect address in memory. Only a base register could be selected in the field selector in memory.

Sperry Rand began shipment in June 1962 and produced 96 UNIVAC III systems. 1962 (MCMLXII) was a common year starting on Monday (the link is to a full 1962 calendar). ...

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. FASTRAND was a magnetic drum mass storage system built by Sperry Rand Corporation for their UNIVAC 1100 series computers. ...

See also

• List of UNIVAC products
• History of computing hardware

// The Remington Rand years (1950 to 1955) Calculating devices UNIVAC 60 UNIVAC 120 Computer systems UNIVAC I UNIVAC 1101 UNIVAC 1102 UNIVAC 1103 Peripherals Storage UNISERVO tape drive Display and print UNIVAC High speed printer 600 line/min printer Offline tape handling units UNIPRINTER 10 char/s printer with tape... Computing hardware has been an essential component of the process of calculation and data storage since it became useful for numerical values to be processed and shared. ...

External links

• 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)
• UNIVAC III Remington
• The UNIVAC III Computer
• UNIVAC III Photos
• UNIVAC III installations (serial numbers given where known)
• UNIVAC III Documentation (PDF) on bitsavers.org