The Buses..........

Address bus

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.



Data Bus

An internal pathway across which data are transferred to and from the processor or to and from memory.

Data Bus - A "bus" is the electronic path that data travels in the set-up-box (or in another type of processor and/or computerized device.) The wider the width of the bus the faster the data can travel. The data bus carries the actual electronic signal versus the address bus that carries information concerning where the data needs to go.



Control bus

The physical connections that carry control information between the CPU and other devices within the computer. Whereas the data bus carries actual data that is being processed, the control bus carries signals that report the status of various devices. For example, one line of the bus is used to indicate whether the CPU is currently reading from or writing to main memory.