Phoronix checks the Intel's Core i7 3960X's performance scaling in various operating systems, you can check it out over here.
Using the new Intel Core i7 3960X Extreme Edition Sandy Bridge
processor, Scientific Linux 6.1, Debian GNU/Linux, Debian GNU/kFreeBSD,
and Solaris 11 11/11 were benchmarked when having a different number of
CPU cores enabled to see how well each operating system scales up to six
cores plus Hyper Threading.