Address Bus

An Address Bus is part of a computer bus, used by CPUs or DMA-capable units for communicating the physical addresses of computer memory elements/locations that the requesting unit wants to access (read/write).

The address bus is the set of lines that carry information about where in memory the data is to be transferred to or from. No actual data is carried on this bus, rather memory addresses, which control the location that data is either read from or written to, are sent here.

The speed of the address bus is the same as the data bus it is matched to.
The address bus is the set of wire traces that is used to identify which address in memory the CPU is accessing.

An internal channel from the CPU to memory across which the addresses of data (not the data) are transmitted. The number of lines (wires) in the address bus determines the amount of memory that can be directly addressed as each line carries one bit of the address.

For example, a 20-line address bus represents the binary number 1,048,576 and reaches that number of memory bytes (the size of the address bus in the IBM PC in 1981). A computer with a 32-bit address bus can directly address 4GB of physical memory, while one with 36 bits can address 64GB.