CPUMon is an advanced performance measurement tool. Its combination GUI/device driver make the wide range of processor performance counters present on the Pentium, Pentium Pro and Pentium II/III, easily accessible. You select the two counters you’re interested in, enable them via the GUI, and at a later point stop the counters in order to see their values. While a measurement is in progress you can watch the values change with NT's built-in Perfmon.
A utility for your NT Tool box.