Computer BusComputer is a wire or a collection of wires that transmits information or power within the computer. The transmission can be either between the computer components or between the computers as well. In short buses are path for data transmission between computer components. In industrial computers buses serve as the functional parts that maintain the communication of the entire network and support it as a single unit.

Bus Parts

A bus is consists of two parts that allow it to function. One part is the address bus. Address bus contains the address of the destination to which data is to be transmitted. Address bus is the controller that directs the bus to transmit the data at particular location. Other is the data bus that carries the actual data to be transmitted. Some important Bus specifications include bus types, bus width, and data transfer rates. Data rates are defined by the rate at which a bus transfers the data.

Bus width

The data transfer rates of buses are based on bus size. Bus size is also termed as bit size. Bit size is the number of pathways a bus uses to send data and defines the bus width. Bus width is the number of bits that a bus can transfer at a time. In short a bus width define the bus size. A bus with bus width of 16-bits can handle 16-bits at a time.

Bus Types / Standards

Since the evolution of computer buses various types of buses or bus standards are being developed. But overall buses can be divided in two categories, one is serial and other is parallel. Parallel Bus: parallel buses can transfer many bits simultaneously. This allows them to send data words on multiple wires or pathways. Skew is the major problem associated with parallel bus at higher data rates. Skew means on parallel wires all the bits do not reach at destination at same clock rate. Serial Bus: serial bus transfers the data bi by bit. Serial bus solves the problem of skew associated with parallel bus. So it can work finer for higher data rates. Along with the address and data bus a serial bus can be associated with power, control and data connections, or differential drivers.

Internal and External Computer Buses

Apart from parallel and serial computer buses are also available as internal and external. Parallel and serial buses are further sub categorized as parallel internal and external computer buses, and serial internal and external computer buses. Internal buses are known as local buses as they connect the components within the computer such as the bus between CPU and internal memory. External buses are used to connect external peripherals such as CD-ROM. Parallel internal computer buses include ISA, EISA, VESA local bus, PCI, MCA (micro channel), low pin count, NuBus, Multibus for industrial systems, S-100 bus, VME bus, SBus, and MBus. Parallel external computer buses include advanced technology attachment (ATA), High Performance parallel interface (HPPI), GPIB, HPIB, PC card standard, Centronics parallel, and SCSI. Serial Internal Computer buses include PCI express (PCIe), Serial Peripheral Interface (SPI) bus, I2C, Hyper-Transport, and 1-wire. Serial external buses include Serial ATA, Universal Serial Bus (USB), Serial Storage Architecture (SSA), Serial Peripheral Interface (SPI), Controller area network (CAN), Fibre Channel, FireWire, Access Bus, RS-485, and apple desktop bus (ADB).