Single chip processing system utilizing general cache and microcode cache enabling simultaneous multiple functions

摘要

A microcode cache memory is provided on a processor chip for supplying frequently used microcode instruction words to a processor. A bank of multiple Tag-Status RAMs holds addresses of microcode words residing in a bank of Data RAMs. A state machine and a special Least Recently Used Random Access Memory (LRU RAM) operate to maintain the more frequently used words in the Data RAMs so that more hits occur to provide the requested word in one clock cycle. A 90 bit microcode word with 20 fields enables the processor to perform multiple functions simultaneously in parallel.