Dual core or upto 8 or 32 cores should be enabled or working provided you have them in the pc / PSC (Personal Super Computer) you are using.
What might be what you are looking for is the /etc/make.conf edits to get a bit more speed out of SL.
Examples:
-march=nocona for core2duo
-march=prescott for dual core laptops intel / intel 805 to 975 cpu's socket 775 / socket 479 mobile.
-march=???? k8 or something like this for amd no clue here.
-pipe
-O2 as in caps letter o , not zero
MAKEOPTS=" -j16 " for intel t2600 core duo laptop cpu works well or "-j20" for quad core but could be higher as this is tested and found safe with this cpu's.
Just google for make.conf or gentoo.org forums / wiki for your cpu to get some examples of tested settings.
/etc/init.d/rc has a parallel on startup and setting this to yes will give a bit more speed during boot up.
Next to time top right is kpowersave thingy and setting this to performance would get the cpu from running at default 50% or lower to running actual speed it was build for.
PS> USE ANY OF THIS AT OWN RISK AND AFTER PROPPERLY RESEARCHING THE CORRECT INFO REGARDING THIS AS IT CAN CAUSE PROBLEMS , HAVE YOU BACKED UP YOUR DATA LATELY ??
Hope this helps.

