High resolution timing with low resolution clocks and microsecond resolution timer for Sun workstations

When tuning operating system and network code, profiling programs, analyzing message interarrival times, and accurately measuring device characteristics, a high resolution clock is often indispensable, as one cannot measure service time distributions without one. This note describes a microsecond clock that we designed and built for Sun 3 and Sun 4 workstations 1 . One can measure average service times without a high resolution clock. This paper explains how to measure average times with high precision in the absence of such a clock. We pose and answer the question: "how many measurements are needed to report timing data to three significant digits?"