The Pentium M was well know for having a very speedy architecture that performed better than faster clocked chips like the Pentium 4. The Pentium M is also a more expensive chip to manufacture and has many power conservation features needed in laptops. In general (warning: very simplified) the fewer clock cycles that you want any given instruction to execute in, the more transistors you have to dedicate to that instruction, and the CPU has a finite number of transistors to utilized. In this case I think that the chip’s efficiency and 2meg cache is having a very pronounced positive effect on the laptops performance.
Measurements like MIPS (Millions of Instructions Per Second) and FLOPS (Floating Point Operations Per Second) do not have a direct correlation to a CPU’s clock speed, as a single operation can take from one clock cycle to over twelve clock cycles to complete. Instructions very from chip set to chipset also. Even within the Pentium family instructions can be different and take different number of cycles to complete. If you want a starter page with info on the Pentium M try this one for more info :
http://en.wikipedia.org/wiki/Pentium_m