The 2630qm is a quad core. It has something called turbo boost where it can dynamically adjust the frequencies (overclocking) without you doing anything.

Thus the 2630qm can be (depending on what is best for the situation)
2.0 Ghz always quad (if you keep the cpu on energy saving mode)
or
2.6 GHz quad core
2.8 GHz dual core
2.9 Ghz single core

The 2670qm is the newer version of this chip with the following speed bump
2.2 Ghz always quad (if you keep the cpu on energy saving mode)
or
2.8 GHz quad core
3.0 GHz dual core
3.1 Ghz single core

Now there are better chips out there via intel that are quad cores (all i7 with "qm" and "xm" are quad cores, if the i7 is "m" then it is a dual core) which have the 2700 series, 2800 series, or 2900 series, but they are not worth it. You can spend up to another 1000 dollars in speed for the best of the best 2960XM and the you will only gain another 19% performance. So while there are better chips than the 2630qm and 2670qm they are overpriced.

Pretty much with the i7 2670qm you are getting a chip that performs better than my i7 920 dekstop processor, yet the chip uses about 30% of the energy that my cpu uses. My cpu is 2 years old now, but it has never chocked on anything I thrown at it, and the only time I have gotten over 80% cpu usage was when I was converting one video format to another.