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Hot Box - CSIRAC Computer, Mercury Delay Line Arithmetic Registers, 1954-1964 Object Reg. No: ST 044232

CSIRAC arithmetic registers delay line 'hot' box contains short mercury delay lines. It is called a 'hot' box, because it was temperature controlled, since a variation in the temperature would affect the timing in the delay lines and prejudice the operations of the computer.

In Sydney originally, the delay lines were not in a temperature controlled box. Sometime before the move to Melbourne, the mercury delay lines were placed inside the temperature controlled box.

The arithmetic registers delay line 'hot' box is different from the main memory, which includes a 'hot' box containing long mercury delay lines.

A register provides a means of storing numbers or other pieces of information, which are currently involved in computation. In CSIRAC, the arithmetic registers consisted of short mercury delay liines, which operated in the same manner as the longer mercury delay lines in the main memory. There also were registers for input and output and these consisted of flip flop circuits or switches on the console. They were not included in the box; no processing occurred in these registers, unlike the arithmetic registers.

All the units in CSIRAC were there to support the processing of data carried out in the registers under the control of the arithmetic unit.

CSIRAC at Melbourne consisted of two rows of cabinets, a control console, input and output devices, test equipment and an off-line paper tape editing area. There were nine cabinets, five in the front row and four in the back. Cool air was blown up through all the cabinets from the basement below. The auxiliary memory (disk drive) occupied the space that would have been occupied by a cabinet in the back row.

The five front row cabinets contained (viewed from left to right from the front) power supplies, input and output circuitry, clock and control circuits, arithmetical circuits and memory control circuits. The four back row cabinets contained (viewed from left to right from the front) power supplies, auxiliary store control circuits, 'disk drive', auxiliary test power supplies and memory control circuits.

The date range (1954 - 1964) is given to indicate that changes were made to the structure and circuitry over the period of CSIRAC's working life..
Acquisition Information:
Donation from Commonwealth Scientific & Industrial Research Organisation (CSIRO), 1965
Discipline: Technology
Dimensions: 24 cm (Height), 42 cm (Width), 112 cm (Length)

More information

Tagged with: computers, computing, csirac computer, making history - csirac
Themes this item is part of: The significance of CSIRAC, 1949 - 1964, Information & Communication Collection, CSIRAC Collection
Primary Classification: COMPUTING & CALCULATING
Secondary Classification: Digital Computing
Tertiary Classification: media & storage
Commissioned By: Commonwealth Scientific & Industrial Research Organisation (CSIRO), Sydney, New South Wales, Australia, 1954 or later
User: University of Melbourne (The), Parkville, Victoria, Australia, 1955-1964
  1. [Book], Mr Peter Thorne, Dr Doug McCann, The Last of the First CSIRAC: Australia's First Computer, Department of Computer Science and Software Engineering- The University of Melbourne, Melbourne, 2000, 2000, 10, 11 Pages
  2. [Book], Mr Paul Doornbusch - University of Melbourne (The) Computer Science Department, the music of csirac, Common Ground Publishing, Australia, Melbourne, 2005, 2005

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