Core i7 920 has lower clock speed and it can get the same clock speed as Phenom II 940 when overclocked. Therefore, i7 overclocks better than Phenom II

Furthermore, Core i7 920 outperforms Phenom II 940 by %22 at stock. So, the difference should be even bigger at the same clock speed
http://www.tomshardware.com/reviews/...0,2114-10.html

Also, take into consideration that many application/games don't use the full power of the 8 threads