BUS LINES

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BUS LINES

• Provide data pathways that connect various system
  components.

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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

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• - 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.

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• 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.
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Types of Buses

• System bus
• Connects the CPU to main memory on the system
  board
• Expansion bus
• - Allows the CPU to communicate with peripheral
  devices.
• Types of expansion buses
• ISA, PCI, AGP, USB, and HPSB

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Types of expansion buses

• 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.

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• 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.

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• 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

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• 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.