VUP stands for VAX Unit of Performance. It is an OpenVMS DCL script originally designed to measure performance of VAX systems.
The benchmark involves a lot of OpenVMS system activity like mode and context switches. In this sense it is different from the usual CPU benchmarks. The result includes not only the plain computational speed, but also the performance of the system activity.
The original DCL procedure was sometimes hanging in a infinite loop on fast CPUs. It has been improved by Volker Halle.