Not to be confused with a mode of public transportation, a bus in tech is an internal electrical pathway that is used by signals travelling from one part of a computer to another.
Modern PCs have processors designed with several different pathways. The internal data travels between memory and microprocessor, while the control sends control unit signals.
Additional parts, like the expansion bus, connect the processor to a computer’s expansion slots.
Technipages Explains Bus
Each pathway within a computer serves a specific purpose, and multiple ones can be active simultaneously. If, for example, internal data and control both need to send signals at the same time, their parallel row wiring allows for the data to travel at the same time. Data is transmitted in bits, and an address-system is used in order to determine what is sent where, or more specifically which target region should receive and/or store the data that is being transmitted.
In early machines, the term bus referred to physical electrical wires that were run parallel to each other. ‘Bus’ has since evolved to describe any physical arrangement that provides the same logical function as those original wires did. As mentioned, they can run and be active simultaneously and in parallels, but can also be daisy-chained together.
Either way, the principle is the same. An important part of the system are address busses. In a 32-bit system, an address bus can be aimed at 4,294,967,296 (or 2^32) locations. Assuming each memory location can hold one byte, the available memory space in total is 4GB. Larger and smaller memories are possible, and the amount of addresses is affected accordingly.
Common Uses of Bus
- Electrical and data busses send back and forth signals via parallel or sequential cabling.
- In modern systems, busses describe more than just parallel wires – it refers to architecture that fulfils the same purpose.
- Without address busses, systems would not know where to aim a transmission.
Common Misuses of Bus
- Data busses can only run sequentially, not concurrently.