back side bus (BSB)

A back side bus (BSB) is a bus used in personalcomputers that connects the central processing unit( CPU) with the level 1 cache and the level 2 cache or an external cache.

In contrast, the Front Side Bus( FSB) connects the central processing unit with the main memory( RAM). Both buses, the frontside and the backside bus, can be used simultaneously, which results in the processor being able to perform more operations during clock time. On some CPUs, such as the Pentium Pro, the backside bus to the L2 cache operates at the same clock rate as the processor; on other processors, the backside bus is clocked at half the clock rate of the processor.