I don't think there's a fundamental difference, but until 2006, Intel's Pentium 4 and Pentium D's "Netburst" architecture (the way a processor operates) was completely different from AMD's chips. These chips were focused solely on clock speed but at the cost of efficiency and true speed. That's why Pentium 4s at over 3.4GHz can't even match an AMD Athlon.Currently, however, Intel's Core 2 Duos are the fastest consumer chips on the planet and are pretty cost efficient and fairly low voltage. Hope that helps a little bit!