The purpose of this article is to present measurements and some analysis of the distribution of interrupt-level timing glitches observed over a period of months in an instrumented dual-processor DEC VAX 6520 running VMS 5.4 with Symmetrical Multiprocessing. Each of the two CPUs is rated at 13 VUPs (VAX Unit of Processing), for a total of 26 VUPs. (A VUP is about half a MIP.) As the instrumented machine was in general use, no active experiments were attempted. These glitches translate into unavoidable gaps in the execution of user-level processes. The gaps are harmless unless the processes have deadlines
['Joe Gwinn']
Some measurements of timeline gaps in VAX/VMS