"psrinfo -pv" only prints the core information on systems running OpenSolaris or Solaris Express, because psrinfo was enhanced by this CR:
6316187 Need interface to determine core sharing by CPUs
which was never backported to a Solaris 10 update.
So I googled for psrinfo opensolaris and found this perl script.
Here's the ouptut of running this perl script on a T5220 server:
$ perl psrinfo.pl -pv
The physical processor has 4 cores and 13 virtual processors (-50)
Another command to get the number of cores is:
kstat cpu_infogrep core_idsort -uwc -l
The core has 4 virtual processors (0-3)
The core has 3 virtual processors (16-18)
The core has 3 virtual processors (32-34)
The core has 3 virtual processors (48-50)
UltraSPARC-T2 (clock 1415 MHz)