The motherbard is the main system board for the PC and provides the data highway (or bus system) that moves data between components on the motherboard and the PC's processor. The speed of the data moving along the bus is measured in megahertz (MHz). Motherboard bus speeds continue to increase with each new motherboard and chipset.
At one time, the motherboard was never considered the limiting factor in a PC configuration. But, with the advance of PC memory and processors, a computer with an older motherboard has only few options as far as upgrading. Newer memory modules and processors may not be compatible with legacy motherboards.
Even though how fast a computer can work with data is dependent on the computer's processor, the motherboard should be determined by the features that the motherboard's chipset provides. The chipset is what determines the capacity for the bus speed. Chipsets provide DMA support and other features such as Accelerated Graphics Port, AGP, which boosts performance.