The feature is new in the Solaris Express 4/04 release.
The CPU Performance Counter (CPC) system gives better access to the performance analysis features available on SPARC and x86 processors.
The CPC commands, cpustat and cputrack, have enhanced command-line syntax for specifying CPU information. In previous versions of the Solaris OS, you were required to specify two counters. The configuration of both commands now enables you to specify only one counter. For simple measurements, you can even omit the counter configuration.