Digital Equipment Corporation

Richard E Calcagni

George M Uhler

William J Grundmann

A high-performance, pipelined CPU in which an improved method is used for saving registers in memory upon the occurrence of a procedure CALL or RETURN. The registers which need to be saved are defined by a bit-mask, and the number of bits is counted by a hardwired circuit, in each machine cycle, producing an output in the form of an offset from a stack pointer which represents the highest memory location needed to save the registers being used. Then a memory probe can be done to see if this location is writable. Thus, in one microinstruction cycle, the count is made and the memory probe can begin.

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Hudson, MA, United States of America

Richard E Calcagni