As default all available CPU's are managed by SQL and on one of my customers Virtual Windows 2008 R2 x64 server (Central site with 40000 clients) i have seen that CPU0 is running very high 80-90% and CPU1 around 50% and the last two barely at all.
Default setting as above!
After my change in SQL2008 Server Management Studio.
This was the dramatic change. CPU0 was down to normal and could execute more SCCM processes and CPU3 and 4 was forced to run SQL2008R2.