non BE processors are overclocked by turning up the front side bus frequency, resulting in other parts being overclocked as well... because the entire motherboard has to be in sync with the fsb. the ram will get overclocked, the northbridge... etc
BE processors have an unlocked multiplyer, where you can turn that up and down to change the speed of the processor without touching the fsb. allows you to overclock the processor freely and leave everything else alone