P4 = teh suxx0r
The Pentium 4 was a "marketing" processor - intentionally crippled so they could crank the clock speeds up high. In all actuality, on a GHz to GHz basis, the P3 actually outperformed the P4. A P4 1.5GHz was about speed eqivalent to a P3 1GHz processor.
Why does this matter?
Well, Intel took the P3, slapped in some minor upgrades, screwed around with some low-power functionality, and slapped the Centrino label on it. I'm running a Centrino @ 1.6GHz that beats the pants off of a 2.4GHz laptop sitting next to it.
"Here at Ortillery Command we have at our disposal hundred megawatt laser beams, mach 20 titanium rods and guided thermonuclear bombs. Some people say we think that we're God. We're not God. We just borrowed his 'SMITE' button for our fire control system."