Communications of the ACM

next chair of the computer science division at Berkeley, we decided to go for it, because that gave us a deadline.

You handed off chapters to one another
via FedExed floppy disks.

DAVID: We prototyped the book as if it were a computer, with an alpha and a beta version.

Microsoft’s David Cutler bought copies
for all members of his design team.

DAVID: I think Microsoft also kept a copy in the stationery store. Pads of paper, pencils, Hennessy and Patterson…

JOHN: In the first year, we probably sold as many books to practicing engineers as we did to the academics. That’s really unusual. Books usually divide one way or the other—either they’re written for professionals or for the university market.

DAVID: The book made those ideas accessible to lots of people.

You also invented a brand new param-
eterized architecture for the book called
DLX that expressed your approach.

DAVID: There are lots of RISC instruction sets, and John is associated with one and I’m associated with another. From a textbook writer’s perspective, we thought that picking one might flavor the book, so we decided to invent a brand-new instruction set.

MIPS lost out to Intel in the PC market,
but RISC processors now power nearly

project,

but you’ll never get these ideas to work in real machines that people want to sell to customers.”

What were the most common objec-
tions?

JOHN: We built academic prototypes, and they didn’t have everything you’d need for a commercial machine. And people said, “When you put in virtual memory support, or support for floating point, all the advantages you have will disappear.”

DAVID: The conventional wisdom at the time was software was buggy because the vocabulary of the computers it talked to was too low. So there were all these efforts to try and make the vocabulary closer to that of the languages. John and I were arguing the opposite, and that was part of the heresy.

JOHN: I think the other thing that undermined it was that we didn’t have a good scientific explanation of what was happening until later. That was part of our motivation to write the book, so that we could explain the ideas quantitatively and scientifically.

You’re referring to Computer Architec-
ture: A Quantitative Approach, which
was first published in 1989 and is now
in its sixth edition.

DAVID: I think a lot of faculty are unhappy with the textbooks they use. John and I talked about it at meetings, and when I realized I was going to be the