Oracle Solaris 10: 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 all of the time. 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, see the proc(4) man page.