The data bus is the "pathway" that allows information and commands to be shared between components. The CPU controls what can be sent on the bus, and uses it to access memory, drives, and expansion cards. Physically, it consists of traces (conducting pathways etched into the chip) embedded in the motherboard's circuit board. It is characterized by the amount of information it can transmit simultaneously. This is known as the "width" of the data bus. Older machines have an 8-bit bus. This means they can carry only a byte at a time between devices. Common AT-class machines have a 16-bit bus, able to transmit two bytes at a time. The latest machines use a 32-bit data bus.
The size of the bus is important because only one device can be on the bus at any one time. For some applications, this can become a tremendous bottleneck. The more information that can be sent through the computer, the faster the machine can function.
