LINDSAY@TL-20B.ARPA (03/09/86)
People who would like to read further might try Husson's excellent book on microprogramming, which I read in 1970 or thereabouts. He discussed real live implementations, including one where you could whip up microcode on a standard 80-column keypunch machine. Then there was the Interdata Model 4, which I thought to be the best minicomputer on the market ( in 1968, before the PDP-11 ). They offered custom microcode: you provide the bit pattern, and they would weave it, by having wires that did (or did not) pass through little U-shaped things. I believe it worked on a principle of transformer coupling. IBM probably had a similar technology, in which case it will be covered in Husson. Don Lindsay -------