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CSIRAC
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==Design== The machine was fairly representative of first-generation [[Vacuum tube|valve]]-driven computer designs. It used [[Mercury (element)|mercury]] [[Delay-line memory|acoustic delay lines]] as its primary data storage, with a typical capacity of 768 20-[[bit]] words, supplemented by a parallel [[Disk storage|disk-type device]] with a total 4096-word capacity and an access time of 10 milliseconds. Its memory clock ran at 1000 [[hertz|Hz]], and the [[control unit]], synchronized to the clock, took two cycles to execute an instruction (later the speed was doubled to one cycle per instruction). The [[Computer bus|bus]] (termed the "digit trunk" in their design){{sfn|McCann|Thorne|2000|pp=8β11, 13, 91}} is unusual compared to most computers in that it was [[Serial communication|serial]]βit transferred one bit at a time. Most of CSIRAC's approximately 2000 valves were of the types [[6SN7]],<ref>6SN7 Double triode, 8-pin, 3.8 W heater</ref> [[6V6]],<ref>{{Cite web |url=http://www.nj7p.org/Tube4.php?tube=6V6 |title=6V6 Beam Power pentode, 8-pin, 2.8 W heater |access-date=2007-01-19 |archive-url=https://web.archive.org/web/20060927064325/http://www.nj7p.org/Tube4.php?tube=6V6 |archive-date=2006-09-27 |url-status=dead }}</ref> EA50 diodes and [[KT66]].<ref>KT66 Beam tetrode, 8-pin, 8.2 W heater</ref> George Semkiw later redesigned the drum-read electronics to use [[germanium]] [[transistor]]s.{{Citation needed|date=May 2025}} Input to the machine was performed in the form of punched {{convert|3|in|mm|adj=on}} wide, 12-track [[paper tape]],<ref>{{cite web| url = https://www.computerhistory.org/revolution/birth-of-the-computer/4/92/363| title = CSIRAC paper tape (replica)| date = 2010| publisher = [[Computer History Museum]]| access-date = 13 October 2023 }}</ref> after experiments with [[Punched card|punch cards]] proved unsatisfactory. The machine was controlled through a console which allowed programs to be stepped through one instruction at a time, and featured [[CRT display]]s which showed the contents of registers. Output was through a standard [[teleprinter]] or to punch tape.{{Citation needed|date=May 2025}} The [[instruction set]] supported the basic set of arithmetic and logical operations, as well as conditional and relative jumps (making it possible to write a library of subroutines). Instructions consisted of three components: a 5-bit "destination" P1-P5, a 5-bit "source" P6-P10, and a 10-bit "address" P11-P20. For instructions that used the main store, the six bits P15-P20 selected one of the 64 logical delay lines. Bits P11-P14 determined the time at which 20 bits of data were written to or extracted from the delay line, and thus represented address of a word within the selected delay line. There were 32 destination gates and 32 source gates; the 10 address bits identified a data word within the store if either the source or destination required access to the store. The total number of source and destination combinations, or different instruction functions, was 1024, although only about 256 of these were used often.<ref>{{cite web|url=http://www.cis.unimelb.edu.au/about/csirac/design.html|title=CSIRAC design|access-date=2018-04-14|archive-date=1 April 2018|archive-url=https://web.archive.org/web/20180401100256/http://www.cis.unimelb.edu.au/about/csirac/design.html|url-status=dead}}</ref> The machine had three 20-bit registers (A, B and C), two of which were involved in multiplication, one 10-bit register which could link to either half of a word, and a group of 16 20-bit registers, addressed via bits P11-P14. In addition the 20-bit program counter (S register), and the instruction register (K) were accessible.{{Citation needed|date=May 2025}} The machine, like all machines of the era, had no [[operating system]]. A high-level interpreted [[programming language]] called INTERPROGRAM was developed in 1960 by Geoff Hill. It was similar to early forms of [[BASIC programming language|BASIC]], which was designed in 1963 for the 20-bit transistorized [[GE-200 series]].{{Citation needed|date=May 2025}} In 1950 CSIRAC was used to play music, the first known use of a digital computer for the purpose. The music was never recorded, but it has been accurately reconstructed.<ref name="beebmus"/><ref name=":0"/><ref name="abc.net.au/radionational/sum-of-all-parts/13.1">{{cite web |last1=Werner |first1=Joel |title=13.1 Electronic music's origin story [BONUS] |url=https://www.abc.net.au/radionational/programs/sum-of-all-parts/13.1-electronic-music%E2%80%99s-origin-story/11422534 |website=[[Radio National]] |publisher=[[Australian Broadcasting Corporation]] |access-date=13 May 2021 |language=en |date=16 August 2019}}</ref><ref name="Early Computer Music Experiments in Australia, England and the USA" /><ref name="Doornbusch"/><ref>{{Cite web |last=Doornbusch |first=Paul |date=26 June 2016 |title=How Australia played the world's first music on a computer |url=https://theconversation.com/how-australia-played-the-worlds-first-music-on-a-computer-60381 |website=The Conversation}}</ref> [[Image:CSIRAC.jpg|right|thumb|CSIRAC, side view]] In 1955, with the [[Commonwealth Scientific and Industrial Research Organisation|CSIRO]]'s decision that computing research was outside its purview, the machine was transferred from its home at the Radiophysics Laboratory at the CSIRO in Sydney, to the [[University of Melbourne]], where it formed Australia's only academic computing facility until late 1956. Many pioneers of computer use in Australia{{who|date=August 2014}} had their first exposure to computing there.{{citation needed|date=August 2014}}
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