FSB stands for Front Side Bus, and is the bus that connects the CPU to the RAM on the motherboard. I/O Buses, which connect the CPU with the systems other components, branch off of the Front Side Bus.

In AMD Systems, The FSB has been supplemented by the HyperTransport Bus.

The FSB is also called by a variety of other names, such as Front Side Bus, Memory Bus, Local Bus, and Host Bus.