Uploaded December 2025 | Updated September 2026, 2 weeks ago
ARCTURUS was a, fixed-point, binary, parallel, single address, general-purpose digital computer using packaged diode-transistor circuits, ferrite-core memory and paper-tape peripheral units. Having a word length of 20 bits, it had 32 distinct instructions with a 13-bit address, enabling 8192 words to be directly addressed. A single-length number consisted of a sign bit and 19 magnitude bits, allowing for a double-length number. A two’s complement representation of negative numbers was used. ARCTURUS could also do Indirect addressing.
David Wong was the System designer, functional designer and logical designer as well as the key programmer for the project. Kevin R. Rosolen played a major role and was responsible for circuit design, constructional techniques and was directly responsible for the construction of the tape reader, the modifications to the printer, the wiring of a large number of packages, all the base wiring of ARCTURUS and all the mechanical construction.
The ARCTURUS project was carried out with extremely limited man-power and financial support (just two people). By salvaging semiconductors and connectors from old equipment, and by constructing several peripheral units in the laboratory, this computer was produced with a component cost of less than $AU10,000 (circa 1966, approximately AU$100,000 in today's money). This sum was obtained over a period of about five years, through the School of Electrical Engineering, at the University of Sydney, as part of David Wong’s PhD research.
Because of the limited funding and personnel involved, ARCTURUS took a long time to design and construct. In late 1963, the input-output console for ARCTURUS was designed, built and tested. In early 1964, the circuitry for the ferrite-core store was designed, constructed and tested. Kevin recalls in this episode how the purchase of the core memory consumed the entire budget for that year. By mid 1964, the specification of the arithmetic and control unit of ARCTURUS was completed, and by late 1965, it was constructed. Unusually, packages within ARCTURUS were given temperature and vibration tests to prove they would be reliable. Dry joints and temperature-sensitive components were identified and corrected. Noise and interconnections were also addressed for high reliability.
ARCTURUS was operational in May 1966, and David Wong provided a presentation entitled "The Design and Construction of the Digital Computer ARCTURUS" at the Proceedings of the Third Australian Computer Conference, Canberra, May 1966.
The main objective of the ARCTURUS Project was the construction of a computing system for research purposes & as a teaching tool. ARCTURUS was designed to assist with complex digital computer control systems and to provide a platform for students to perform research. The ARCTURUS project was regarded as a success in that regard. It was also built for high speed at a low cost.
ARCTURUS featured very high speed logical circuits and was the fastest of all computer arithmetic units constructed in Australia at that time. During its lifespan, it was found to be very reliable. This was due to its functional packaging, ground planes and special mounting arrangements for important signal lines, which were all examples of the techniques established by David and Kevin. ARCTURUS had an arithmetic unit which made extensive use of a “high speed carry-lookahead-adder” which could be used to accumulate numbers in 0.5 microseconds. ARCTURUS’s featured ferrite-core memory, which used the coincident-current-selection method. Access to the memory was extremely fast for the day.
ARCTURUS was used to do research work on the processing of recordings from radio telescopes. It also supported several Electrical Engineering Honours projects. These were concerned with a digital differential analyser simulator and a floating-point coding system similar to the A9 system used with SILLIAC and the KDF9. It was also used as a logic simulator for testing the design of a digital control system. ARCTURUS was also to be used in experiments in efficient communication between computers.
All programs for ARCTURUS were written in binary until the development of API language. Instructions in API used the sexadecimal character set and contained 57 words.
ARCTURUS was the final of three major contributions by David Wong and Kevin Rosolen to the history of computing in Australia. It was a culmination of many lessons learnt on SNOCOM & NIMBUS. Ultimately, what it proved was that a small but effective research group could produce world-class computing right here on our shores. This group showed that it was capable of taking full advantage of progress in computer technology and of establishing advanced concepts and techniques. David Wong prophetically goes on to say in his thesis, “Computers have assisted in research and development, and in the field of artificial intelligence, where they have provided an understanding of human mental processes.”
ARCTURUS was a, fixed-point, binary, parallel, single address, general-purpose digital computer using packaged diode-transistor circuits, ferrite-core memory and paper-tape peripheral units. Having a word length of 20 bits, it had 32 distinct instructions with a 13-bit address, enabling 8192 words to be directly addressed. A single-length number consisted of a sign bit and 19 magnitude bits, allowing for a double-length number. A two’s complement representation of negative numbers was used. ARCTURUS could also do Indirect addressing.
David Wong was the System designer, functional designer and logical designer as well as the key programmer for the project. Kevin R. Rosolen played a major role and was responsible for circuit design, constructional techniques and was directly responsible for the construction of the tape reader, the modifications to the printer, the wiring of a large number of packages, all the base wiring of ARCTURUS and all the mechanical construction.
The ARCTURUS project was carried out with extremely limited man-power and financial support (just two people). By salvaging semiconductors and connectors from old equipment, and by constructing several peripheral units in the laboratory, this computer was produced with a component cost of less than $AU10,000 (circa 1966, approximately AU$100,000 in today's money). This sum was obtained over a period of about five years, through the School of Electrical Engineering, at the University of Sydney, as part of David Wong’s PhD research.
Because of the limited funding and personnel involved, ARCTURUS took a long time to design and construct. In late 1963, the input-output console for ARCTURUS was designed, built and tested. In early 1964, the circuitry for the ferrite-core store was designed, constructed and tested. Kevin recalls in this episode how the purchase of the core memory consumed the entire budget for that year. By mid 1964, the specification of the arithmetic and control unit of ARCTURUS was completed, and by late 1965, it was constructed. Unusually, packages within ARCTURUS were given temperature and vibration tests to prove they would be reliable. Dry joints and temperature-sensitive components were identified and corrected. Noise and interconnections were also addressed for high reliability.
ARCTURUS was operational in May 1966, and David Wong provided a presentation entitled "The Design and Construction of the Digital Computer ARCTURUS" at the Proceedings of the Third Australian Computer Conference, Canberra, May 1966.
The main objective of the ARCTURUS Project was the construction of a computing system for research purposes & as a teaching tool. ARCTURUS was designed to assist with complex digital computer control systems and to provide a platform for students to perform research. The ARCTURUS project was regarded as a success in that regard. It was also built for high speed at a low cost.
ARCTURUS featured very high speed logical circuits and was the fastest of all computer arithmetic units constructed in Australia at that time. During its lifespan, it was found to be very reliable. This was due to its functional packaging, ground planes and special mounting arrangements for important signal lines, which were all examples of the techniques established by David and Kevin. ARCTURUS had an arithmetic unit which made extensive use of a “high speed carry-lookahead-adder” which could be used to accumulate numbers in 0.5 microseconds. ARCTURUS’s featured ferrite-core memory, which used the coincident-current-selection method. Access to the memory was extremely fast for the day.
ARCTURUS was used to do research work on the processing of recordings from radio telescopes. It also supported several Electrical Engineering Honours projects. These were concerned with a digital differential analyser simulator and a floating-point coding system similar to the A9 system used with SILLIAC and the KDF9. It was also used as a logic simulator for testing the design of a digital control system. ARCTURUS was also to be used in experiments in efficient communication between computers.
All programs for ARCTURUS were written in binary until the development of API language. Instructions in API used the sexadecimal character set and contained 57 words.
ARCTURUS was the final of three major contributions by David Wong and Kevin Rosolen to the history of computing in Australia. It was a culmination of many lessons learnt on SNOCOM & NIMBUS. Ultimately, what it proved was that a small but effective research group could produce world-class computing right here on our shores. This group showed that it was capable of taking full advantage of progress in computer technology and of establishing advanced concepts and techniques. David Wong prophetically goes on to say in his thesis, “Computers have assisted in research and development, and in the field of artificial intelligence, where they have provided an understanding of human mental processes.”
