Could be that you've got an i7. I'll stick my 4770K in this later and try.
Probably is that. I get cpu bottlenecking with an i7. Let us know what difference it makes.
What were you using, an i5?
Could try turning off Hyper-threading in the BIOS and see it if helps.
Some older games work better without it.
I doubt its that otherwise id be seeing the same thing with my i7. Also i believe he was using a non HT cpu.