A frontside bus is a communication interface that serves as the main link between the CPU and system memory and other parts of the chipset and motherboard. It was actively used in computer architecture in the 1990s-early 2000s, and because the speed of this communication link could be a bottleneck in computer systems, it was considered an important measure of computer performance.
The FSB connects the following components with the CPU:
Graphics card through the northbridge
Other input/output devices
Techopedia explains Frontside Bus (FSB)
The FSB was a prominent computer architecture component that allowed a CPU to communicate with various computer system resources. It connected the system memory, input/output (I/O) peripherals and other board components to the CPU and acted as the main transport link for data around the computer hardware. However, although the FSB was a very important component, its limited speed also made it a major bottleneck.
FSB speed is measured in hertz (Hz) and is often also expressed as a ratio to CPU speed. For example, a processor running at 2.4 GHz with an FSB of 400 MHz would have a CPU to FSB ratio of 6:1.