In computer parlance, a data bus is a group of electrical wires used to send information (data) back and forth between two or more components.
A data bus has many different defining characteristics, but one of the most important is its width. The width of a data bus refers to the number of bits (electrical wires) that make up the bus. Common data bus widths include 1-, 4-, 8-, 16-, 32-, and 64-bit.
When manufacturers refer to the number of bits a processor uses, such as “This computer uses a 64-bit processor,” they are referring to the width of the front side data bus, the bus that connects the processor to its main memory. Other types of data buses used in computers include the back side bus, which connects the processor to dedicated cache memory.
Early Macs used a 16-bit data bus; the original Macintosh used a Motorola 68000 processor. Newer Macs use 32- or 64-bit buses.
