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SILLIAC (Sydney version of the Illinois Automatic Computer)

Overview

SILLIAC was an early electronic computer built by the University of Sydney, Australia, based on the ILLIAC/ORDVAC design from the University of Illinois. Officially opened on September 12, 1956, it was one of the most powerful computers in the world at the time and brought Australia into the computer age. Its first scientific computation was run by PhD student Bob May, who would later become Robert May, Baron May of Oxford – one of the most influential ecologists of the 20th century. SILLIAC operated for 14 years until May 17, 1968.

Technical Specifications

Specification Detail
Word length 40 bits
Instructions per word Two 20-bit instructions
Main memory 1024 words of 40 bits, Williams tube storage (40 tubes)
Operations ~150 operations on two registers
Performance ~13000 additions/sec; ~1400 multiplications/sec; ~1200 divisions/sec
Architecture Parallel, asynchronous
Initial vacuum tubes 2768 (using 2C51 type from Bell Labs)
Tubes after 1958 upgrade 2911
Valve type 2C51 (developed by Bell Labs for undersea telephone repeaters) – 5x longer lifespan than standard 6J6 at 6x cost
Dimensions 2.5 m high x 3 m wide x 0.6 m deep (main cabinet)
Power consumption 35 kilowatts
I/O Paper tape input at 200 characters/sec; output at ~50 cps; teleprinter at 10 cps
Magnetic tape (1958) Four units added
Reliability Average of 11 hours between failures
Rooms required 3: computer room, power supply room, basement air conditioning room

Design and Construction History

Origins (1953)

In late 1953, two people independently realized the University of Sydney’s School of Physics needed an electronic computer:

  • Harry Messel: The dynamic Canadian physicist who had become head of the School of Physics in 1952, at age 30. He served for 35 years. Messel recognized the need for computing power for nuclear physics research.
  • John Blatt: A newly arrived theoretical physicist.

Rather than design a computer from scratch, Blatt and Messel chose to copy the ILLIAC design. The University of Illinois was happy to share blueprints and assistance; information flowed bidirectionally between the two institutions.

Naming

The name SILLIAC stood for Sydney version of the Illinois Automatic Computer – or, with a wink, the “Silly ILLIAC.” The name acknowledged the machine’s heritage directly.

Funding

Adolph Basser, a jewelry businessman and philanthropist with a love of horse racing and a modest disposition, donated AU 50000 toward the computer. Sir Frank Packer, the media mogul, funded the associated Nuclear Research Foundation.

  • Estimated cost: AU 35200 (approximately ten times the price of a Sydney suburban house)
  • Final cost: AU 75000

Construction

  • July 1954: Standard Telephones and Cables (STC) was contracted to manufacture the computer
  • 1955: Manufacturing began
  • June 1956: SILLIAC completed; first scientific computation run
  • July 9, 1956: Regular user access began
  • September 12, 1956: Official opening in the Adolph Basser Computing Laboratory

Key Design Choice: Bell Labs Valves

Instead of the standard 6J6 vacuum tubes used in ILLIAC and ORDVAC, SILLIAC used 2C51 valves developed by Bell Labs for undersea telephone repeaters. These cost six times more but lasted five times longer – a critical trade-off for a machine at the bottom of the world, far from component suppliers.

What Science Was Done on It

Bob May’s First Computation (June 1956)

The very first scientific calculation on SILLIAC was carried out by PhD student Bob May (later Robert May, Baron May of Oxford). May was trained in theoretical physics by the distinguished physicist Robbie Schafroth and received his PhD at age 24 for work on bosons and superconductivity. He later became one of the most important theoretical ecologists in history, renowned for his work on chaos theory in population dynamics and the stability-complexity debate in ecology.

John C. Butcher (later a celebrated numerical analyst known for Butcher tableaux in Runge-Kutta methods) also used the system in its early days.

Commercial and Government Work

SILLIAC ran Australia’s first computer payroll system for the Postmaster-General’s Department (later Australia Post). Other commercial users included:

  • Woolworths
  • Snowy Mountains Hydro-electric Authority
  • Banks
  • CSIRO Division of Radiophysics (which rented 400 hours of computing time in 1957 for A$16000 – equivalent to ~$568000 in 2022 dollars)

At peak operation, SILLIAC served over 2000 users and operated 24 hours a day.

Scientific Research

Nuclear physics calculations (the original motivation), theoretical physics, and wide-ranging university research.

Notable Anecdotes

  • “Probably the most powerful computer” in the world: At the time of its completion, SILLIAC was described (perhaps with some Australian enthusiasm) as “probably the most powerful computer” the world had seen.
  • Modern comparison: Computational tasks that SILLIAC performed over its entire 14-year lifetime could be completed by a modern smartphone in minutes. Its storage capacity equaled less than one second of an MP3 file.
  • Bob May’s trajectory: The first person to run a scientific computation on SILLIAC became Baron May of Oxford, President of the Royal Society, Chief Scientific Adviser to the UK Government, and a pioneer of chaos theory – a remarkable arc from a vacuum-tube computer in Sydney to the highest echelons of British science.

Decommissioning and Current Status

  • May 17, 1968: SILLIAC was decommissioned and replaced by a faster and larger machine.
  • The machine was dismantled. Surviving fragments are displayed at:
    • Chau Chak Wing Museum at the University of Sydney (opened November 2020)
    • Powerhouse Museum (Sydney)
    • The Australian Computer Museum Society obtained additional components by 2023

Sources

  • “SILLIAC,” Wikipedia. https://en.wikipedia.org/wiki/SILLIAC — Accessed: 2026-04-02
  • “SILLIAC: the machine that brought Australia into the computer age,” University of Sydney. https://www.sydney.edu.au/news-opinion/news/2021/05/05/silliac-the-machine-that-brought-australia-into-the-computer-age.html — Accessed: 2026-04-02
  • “Robert May, Baron May of Oxford,” Wikipedia. https://en.wikipedia.org/wiki/Robert_May,_Baron_May_of_Oxford — Accessed: 2026-04-02
  • “SILLIAC,” Radiomuseum.org. https://www.radiomuseum.org/r/stcaus_silliac_sydney_version_of_the_illinois_automatic.html — Accessed: 2026-04-02
  • “ACS Heritage Project: Chapter 19,” Australian Computer Society. https://50years.acs.org.au/heritage-projects/acs-heritage-project–chapter-19.html — Accessed: 2026-04-02
  • “10: Australia’s first Computers: SILLIAC,” The Synthetic Image. https://the-synthetic-image.com/australias-first-computers-silliac/ — Accessed: 2026-04-02