Bus Speed
The speed at which the main bus, or base clock, works. This term is used for Nehalem-based Intel® processors that are not equipped with an Intel® QuickPath Interconnect.

System Bus
The speed at which the front side bus, or the ring bus interconnect, is working. The front side bus is an older technology used before ring bus interconnect and Nehalem-based Intel® processors.

Operating System:

OS Independent

This applies to:

Intel® Processor Identification Utility