“graduate student” from Stanford (
University)—do you remember what you
were presenting then, John?
JOHN HENNESSY: It was probably the
microcode compiler that I wrote that
got used for (James H.) Clark’s Geometry Engine project.
John, you went back to Stanford and, in
1981, started working on your own Reduced Instruction Set microprocessor,
which you eventually commercialized
as the Microprocessor without Interlocked Pipeline Stages, or MIPS. However, the ideas behind RISC and MIPS
were controversial at first.
JOHN: People said, “This is fine for
DAVID: It’s a dumb way to design microprocessors if you have to repair microcode bugs. That got me thinking
about how to build something simpler
that made more sense for microprocessors.
So during a series of graduate courses
that began in 1980, you began developing a fast, lean microprocessor that included only instructions that were actually used. How did you meet John?
DAVID: There was a (U.S. Defense
Advanced Research Projects Agency)
DARPA meeting at the (University of
California,) Berkeley campus in May of
1980, and I was presenting some of our
AT A TIME when “making an impact” can
feel like a vague or even overwhelming
prospect, it’s worth reviewing the accomplishments of two scientists who
have done just that: ACM A.M. Turing
Award recipients John Hennessy and
David Patterson. What began as a sim-ple-sounding insight—that you could
improve microprocessor performance
by including only instructions that are
actually used—blossomed into a paradigm shift as the two honed their ideas
in the MIPS (Microprocessor without
Interlocked Pipeline Stages) and RISC
(Reduced Instruction Set Computer)
processors, respectively. A subsequent
textbook, Computer Architecture: A
Quantitative Approach, introduced generations of students not just to that particular architecture, but to critical principles that continue to guide designers
as they balance constraints and strive
for maximum efficiency.