Evaluation of interrupt handling routines with a logic state analyser

Use of a logic state analyser as a hardware monitoring tool is described. The interrupt handling routines of the UNIX* operating system, running on a Perkin-Elmer 7/32, were measured before and after major code modification. CLock handling is used as an example. Performance improvements included a reduction in the execution time of the common interrupt handler from 654 to 55 microseconds and a consequent reduction in cLock handling time from 842 to 347 micro-seconds. Measurement methods and performance enhancements are discussed.