The ILLIAC II was a revolutionary super-computer built by the

University of Illinois The University of Illinois Urbana-Champaign (U of I, Illinois, University of Illinois, or UIUC) is a public land-grant research university in Illinois in the twin cities of Champaign and Urbana. It is the flagship institution of the University ...

that became operational in 1962.

Description

The concept, proposed in 1958, pioneered

Emitter-coupled logic In electronics, emitter-coupled logic (ECL) is a high-speed integrated circuit bipolar transistor logic family. ECL uses an overdriven bipolar junction transistor (BJT) differential amplifier with single-ended input and limited emitter current to ...

(ECL) circuitry, pipelining, and transistor memory with a design goal of 100x speedup compared to

ILLIAC I The ILLIAC I (Illinois Automatic Computer), a pioneering computer in the ILLIAC series of computers built in 1952 by the University of Illinois, was the first computer built and owned entirely by a United States educational institution. Compute ...

. ILLIAC II had 8192 words of

core memory Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (manufacturing), used in casting and molding * Core (optical fiber), the signal-carrying portion of an optical fiber * Core, the central ...

, backed up by 65,536 words of storage on

magnetic drum Drum memory was a magnetic data storage device invented by Gustav Tauschek in 1932 in Austria. Drums were widely used in the 1950s and into the 1960s as computer memory. For many early computers, drum memory formed the main working memory ...

s. The core memory access time was 1.8 to 2 µs. The magnetic drum access time was 8.5ms. A "fast buffer" was also provided for storage of short loops and intermediate results (similar in concept to what is now called

cache Cache, caching, or caché may refer to: Places United States * Cache, Idaho, an unincorporated community * Cache, Illinois, an unincorporated community * Cache, Oklahoma, a city in Comanche County * Cache, Utah, Cache County, Utah * Cache County ...

). The "fast buffer" access time was 0.25 µs. The word size was 52 bits.

Floating point In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can be ...

numbers used a format with 7 bits of exponent (power of 4) and 45 bits of mantissa.

Instructions Instruction or instructions may refer to: Computing * Instruction, one operation of a processor within a computer architecture instruction set * Computer program, a collection of instructions Music * Instruction (band), a 2002 rock band from Ne ...

were either 26 bits or 13 bits long, allowing packing of up to 4 instructions per memory word. Rather than naming the pipeline stages, "Fetch, Decode, and Execute" (as on Stretch), the pipelined stages were named, "Advanced Control, Delayed Control, and Interplay".

Innovation

* The ILLIAC II was one of the first

transistorized computers upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch e ...

. Like the IBM Stretch computer, ILLIAC II was designed using "future transistors" that had not yet been invented. * The ILLIAC II project was proposed before, and competed with IBM's Stretch project, and several ILLIAC designers felt that Stretch borrowed many of its ideas from ILLIAC II, whose design and documentation were published openly as University of Illinois Tech Reports. Members of the ILLIAC II team jokingly referred to the competing IBM Project as "St. Retch". * The ILLIAC II had a division unit designed by faculty member

James E. Robertson James is a common English language surname and given name: *James (name), the typically masculine first name James * James (surname), various people with the last name James James or James City may also refer to: People * King James (disambiguati ...

, a co-inventor of the SRT Division algorithm. * The ILLIAC II was one of the first pipelined computers, along with IBM's Stretch Computer. The pipelined control was designed by faculty member

Donald B. Gillies Donald Bruce Gillies (October 15, 1928 – July 17, 1975) was a Canadian computer scientist and mathematician who worked in the fields of computer design, game theory, and minicomputer programming environments. Early life and education ...

. The pipeline stages were named Advanced Control, Delayed Control, and Interplay. * The ILLIAC II was the first computer to incorporate Speed-Independent Circuitry, invented by faculty member

David E. Muller David Eugene Muller (November 2, 1924 – April 27, 2008) was an American mathematician and computer scientist. He was a professor of mathematics and computer science at the University of Illinois (1953–92), after which he became an emeritu ...

. Speed-Independent Circuitry is a class of asynchronous digital logic based on the Muller

C-element In digital computing, the Muller C-element (C-gate, hysteresis flip-flop, coincident flip-flop, or two-hand safety circuit) is a small binary logic circuit widely used in design of asynchronous circuits and systems. It outputs 0 when all in ...

. This digital logic, being asynchronous, runs at full speed of transistor propagation and requires no clocks.

Discoveries

During check-out of the ILLIAC II, before it became fully operational, faculty member

programmed ILLIAC II to search for

Mersenne prime In mathematics, a Mersenne prime is a prime number that is one less than a power of two. That is, it is a prime number of the form for some integer . They are named after Marin Mersenne, a French Minim friar, who studied them in the early 17t ...

numbers. The check-out period took roughly 3 weeks, during which the computer verified all the previous Mersenne primes and found three new prime numbers. The results were immortalized for more than a decade on a UIUC Postal Annex cancellation stamp, and were discussed in the New York Times, recorded in the Guinness Book of World Records, and described in a journal paper in Mathematics of Computation.

End of life

The ILLIAC II computer was disassembled roughly a decade after its construction. By this time the hundreds of modules were obsolete scrap; many faculty members took components home to keep. Donald B. Gillies kept 12 (mostly control) modules. His family donated 10 of these modules and the front panel to the University of Illinois CS department in 2006. The photos in this article were taken during the time of donation. Donald W. Gillies, the son of Donald B. Gillies, has a complete set of documentation (instruction set, design reports, research reports, and grant progress reports, roughly 2000 pages) from the ILLIAC II project. He can be contacted for further details about this computer.http://www.ece.ubc.ca/~gillies
/ref> Most of this documentation should also be available as DCL technical reports in the UIUC Engineering library, although it would not be packaged as a single report.

References

External links