The psradm command can be used to change the operational status of a processor(s) in a multiprocessor system. The statuses are online, offline and no-intr. Here are a few examples.
Take processors 2 and 3 offline # psradm -f 2 3
Processors 1 and 2 are not interrupted by I/O processes # psradm -i 1 2
Bring a specified processor, 3, online # psradm -n 3