Pentium M vs. Pentium 4 processor

I'm looking to buy a new laptop, and see a huge difference in clock speeds between the new Pentium M processrors vs. the Pentium 4 processors. Why is this?

I heard that the Pentium M consumes less power, therefore it's just as fast as the P4 processor. Is this true at all?

Thoughts?

The Pentium M processors (not to be confused with Pentium 4-M), are a new processor family, that is designed specifically for laptops. Since each clock cycle uses battery life, the Pentium M was designed to "do more" with each clock cycle, so that its overall performance would still be on par with the higher clock Pentium 4-M's, while providing longer battery life. In general, it seems to be successful, with the 1.6 Ghz Pentium M being about the same performace as a 2.2 Ghz Pentium 4-M.

The "centrino" technology combines the Pentium M processor with the new 855 chipset and a new wlan adapter.

HTH