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Comments, Queries, Debate: Whirlwind and Microprogramming

IP.com Disclosure Number: IPCOM000129640D
Original Publication Date: 1990-Dec-31
Included in the Prior Art Database: 2005-Oct-06
Document File: 2 page(s) / 14K

Publishing Venue

Software Patent Institute

Related People

Maurice V. Wilkes: AUTHOR [+3]

Abstract

Computer Laboratory Cambridge, England

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THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

Copyright ©; 1990 by the American Federation of Information Processing Societies, Inc. Used with permission.

Comments, Queries, Debate: Whirlwind and Microprogramming

Maurice V. Wilkes

Computer Laboratory Cambridge, England

Richard E. Smith

718 Vermillion Street Hastings, MN 55033

In his article "Historical Overview of Computer Architecture" (Annals, Vol. 10, No. 4, p. 281), R.E. Smith implied that the Whirlwind computer used microprogramming. This is not correct.

In the Whirlwind, the execution of each instruction (except for multiplication which had its own control) took a certain interval of time, the same for all instructions. This interval was divided into eight subintervals. The control unit emitted a sequence of eight control pulses that brought about the execution of the instruction. The sequence of pulses was different for different instructions, but there were always exactly eight, and they occurred in an unvarying sequence. There was no concept of branching within a microprogram, which is a central concept of microprogramming.

The pulse sequences for the various instructions were determined by a diode matrix. Thus, although the Whirlwind did not use microprogramming, it did have a control store. I have described in my paper "The Genesis of Microprogramming" (Annals, Vol. 8, No. 2, pp. 115126) and also in my memoirs (MIT Press, 1984, p. 178) how the Whirlwind control was an important input to the thinking that led me to the concept of microprogramming. Slips occur, and some matter more than others. I think that the above error in a journal of record in the computer history field is important enough to be corrected.

I appreciate the comments by Professor Wilkes about the r...