Clock Speed

• In terms of the speed at which it performs its fundamental operations--in other words, its clock speed--the E6700 is rated at 2.66 gigahertz (GHz). That of the E6660 is slower, as it is rated at 2.4 GHz.
  
  

Bus/Core Ratio

• The E6700 has a 10x multiplier, which means that it measures the ratio of the internal CPU clock rate to the externally supplied clock at 10 to 1. By comparison, the E6600 has a 9x multiplier, thus producing a 9-to-1 ratio.
  
  

Identical CPU

• Despite the two aforementioned differences, the E6700 and E6600 are virtually the same processor. Both dual-core CPUs, each one is manufactured on a 143-square-millimeter die containing 291 million transistors.