This feature is new in the Solaris Express 8/04 release.
In this release, changes have been made to the internals of the load averaging, cpu usr/sys/idle, and accounting functions. Microstate accounting has replaced the old accounting mechanism and is enabled by default. As a result, you might notice slightly different process usage and timing statistics.
Switching to microstate accounting provides substantially more accurate data about user processes and the amount of time they spend in various states. In addition, this information is used to generate more accurate load averages and statistics from the /proc file system.
For more information about process accounting and statistics, see the System Administration Guide: Advanced Administration. See also the proc(4) man page.