To give a comparison to show the validity of the math, I have an Intel Core i7 3930K @ 4.4GHz. That's:
6 (cores) * 4,400 (Million operations/s) / 3375 (ops/hash) = 7.82 MHash/s
Compare this to the 8.7 that I actually see.
What miner are you using? With the Ufasoft miner I remember seeing something like of 25 mhash/s on a 6-core Xeon clocked less than your i7.
That was on an OpenCL miner. I figured it would be closer to the max potential than that. Right now I use my cpu for litecoin anyway, but at those numbers I may switch; probably not worth it even at 66 MH/s, though.
Also, sorry for the bad math. I've edited the original post where I put it. Thanks for the insight.