An
address bus is a
computer bus (a series of lines connecting two or more devices) that is used to specify a
physical address. When a
processor or
DMA-enabled device needs to read or write to a memory location, it specifies that memory location on the address bus (the value to be read or written is sent on the
data bus). The width of the address bus determines the amount of memory a system can address. For example, a system with a
32-bit address bus can address
232 (4,294,967,296) memory locations. If each memory location holds one byte, the addressable memory space is 4 GB.