History Software Engineering

RISC Microprocessors – Reduced Instruction Set Computer CPUs – 1980 AD

Return to Timeline of the History of Computers



David Patterson (b. 1947), John L. Hennessy (b. 1952)

Professor David Patterson at the University of California, Berkeley, studied systemic inefficiencies inside the CPUs of his day and came up with an approach to optimize how computers managed machine instructions: the Reduced Instruction Set Computer (RISC). Many machine instructions were designed in the 1960s to make it easier for humans to program computers in assembly language. But by the 1980s, computers were mostly being programmed in high-level language. Patterson reasoned that the CPU could be radically simplified by removing the instructions that could be useful to a human programmer but not to a machine compiler.

With funding from the US military, Patterson started the RISC project in 1980. The following year a similar project started at Stanford under computer scientist John L. Hennessy. Both projects drew in part from ideas developed in the 1960s for the CDC 6600 by Seymour Cray.

Within a few years, both projects produced their first microprocessors. They were dramatically faster than the so-called Complicated Instruction Set Computers (CISC) on the market, most notably the x86 microprocessors manufactured by Intel. Still, the RISC chips remained a tiny part of the world’s microprocessor market, largely because they couldn’t run most of the software that had been written for Microsoft’s DOS and Windows operating systems.

The Stanford team went on to create MIPS Computer Systems in 1984, a company that developed high-performance microprocessors that were adopted by Silicon Graphics® and (for a time) DEC. But MIPS had trouble competing against Intel, which had far more money to spend on research as a result of its larger customer base.

The big turning point for the RISC idea came in the 1990s, when chipmakers figured out how to put a RISC computer inside a CISC computer. That is, the CPU fetched x86 CISC instructions but translated them into RISC instructions inside the chip. This produced the best of both worlds: a computer that could run the legacy CISC code but had the speed and power advantages of RISC.

Today nearly all computers are RISC.

SEE ALSO Microprogramming (1951), Cray Research (1972), Microsoft and the Clones (1982)

Thirty-seven RISC microprocessors manufactured on a single silicon wafer at the IBM factory of Corbeil-Essonnes, France, February 1, 1992.

Fair Use Source: B07C2NQSPV