php-cgi process use only core at 100% on a 4 core server vps

Hi
This morning i have upgraded my vps from 1 core to a 4 core vps, but I see that each php-cgi process use only one core at the time.

....1 process, core 1
....2 process, core 2
.....n.............n

How I can run 1 php-cgi process at the same time on all 4 cores?

Thanks.
Regards.