A front-side bus (FSB) is a computer communication interface (bus) that was often used in Intel-chip-based computers during the 1990s and 2000s. Computer dictionary definition of what FSB (front-side bus) means, including related links, information, and terms. The FSB was a prominent computer architecture component that allowed a CPU to communicate with various computer system resources. Bus speed usually refers to the speed of the front side bus (FSB), which connects the CPU to the northbridge. The FSB speed of a CPU, which translates into the "front side bus" speed of a " central processing unit," is the speed at which data is processed in a computer.