Microcode: Difference between revisions

Revision as of 17:34, 13 March 2005

Revision as of 18:32, 21 March 2005

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Before 1951, the control logic for central processing units was designed by ''ad hoc'' methods. One of the simplest was to use rings of [[flip-flop]]s to sequence the computer's control logic.

In [[1951]] [[Maurice Wilkes]] had a fundamental insight. He realized that if one takes the control signals for a computer, one could understand them as being played much like a [[player piano]] roll. That is, they are controlled by a sequence of very wide words constructed of bits[[bit]]s.

A microprogram provides the bits to control these. The fundamental advance is that CPU control becomes a specialized form of a computer program. It thus transforms a complex electronic design challenge (the control of a CPU) into a less-complex programming challenge.