Editing Front-side bus (section)

===Memory===

{{see also | Memory divider}}

Setting an FSB speed is related directly to the speed grade of memory a system must use. The memory bus connects the northbridge and RAM, just as the front-side bus connects the CPU and northbridge. Often, these two buses must operate at the same frequency. Increasing the front-side bus to 450&nbsp;MHz in most cases also means running the memory at 450&nbsp;MHz.

In newer systems, it is possible to see memory ratios of "4:5" and the like. The memory will run 5/4 times as fast as the FSB in this situation, meaning a 400&nbsp;MHz bus can run with the memory at 500&nbsp;MHz. This is often referred to as an 'asynchronous' system. Due to differences in CPU and system architecture, overall system performance can vary in unexpected ways with different FSB-to-memory ratios.

In image, audio, video, gaming, [[Field-programmable gate array|FPGA]] synthesis and scientific applications that perform a small amount of work on each element of a large [[data set]], FSB speed becomes a major performance issue. A slow FSB will cause the CPU to spend significant amounts of time waiting for data to arrive from [[random-access memory|system memory]]. However, if the computations involving each element are more complex, the processor will spend longer performing these; therefore, the FSB will be able to keep pace because the rate at which the memory is accessed is reduced.