Definition of Bus lines Also known as buses Connects the parts of the CPU to each other. Buses are used to transfer bits from input devices to memory, from memory to the CPU, from the CPU to memory, and from memory to output or storage devices. All buses consist of two parts; i) data bus ii) address bus
--- -Data Bus measured by its size. - The size of a bus called bus width, which is determines the number of bits that can be transmitted at one time. Example: A 32-bit bus can transmit 32 bits (four bytes) at a time. On a 64-bit bus, bits are transmitted from one location to another 64 bits (eight bytes) at a time. - The larger the number of bits handled by the bus, the faster the computer transfers data.
Highway analogy: - Assume that one lane on a highway can carry one bit. A 32-bit bus, then, is like a 32-lane highway; and a 64-bit bus is like an 64-lane highway.
Types of Buses i) System bus - Connects the CPU to main memory on the system board ii) Expansion bus - Allows the CPU to communicate with peripheral devices. - Types of expansion buses: ISA, PCI, AGP, USB, and HPSB
Types of expansion buses a) ISA (Industry Standard Architecture) - The most common and slowest expansion bus. - A mouse, modem cad, sound card, and low speed network card are examples of devices connect to ISA bus. b) PCI (Peripheral Component Interconnect) - The PCI bus transfers data about 20 times faster than ISA bus. - Most computer today have PCI bus - PCI buses was designed to meet the video demands of graphical user interfaces.
--- C) AGP (Accelerated Graphics Port) - Designed by Intel to improve the speed of 3-D graphics and video performance - AGP is twice as fast as the PCI bus. - AGP is replacing The PCI bus for the transfer of video data. d) USB (Universal Serial Bus) - USB is a bus that eliminate the need to install expansion cards into expansion slots. - USB combines with PCI bus on the system board to support several external devices without using expansion slots or cards.
--- - External USB devices are connected from one to another and then onto the USB bus. The USB bus then connects to the PCI bus on the motherboard. - USB 1.1 – over twice faster than AGP bus. - USB 2.0 – 40 times faster than USB 1.1
--- e) FireWire buses - Also known as high performance serial bus (HPSB). - Operate much like USB buses and perform at speeds comparable to USB 2.0. - Fire Wire and USB 2.0 buses are used for special applications that provide support for digital camcorders and video editing software.