Expansion Buses

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Expansion Buses

• Industry Standard Architecture (ISA)
• Micro Channel Architecture (MCA)
• Enhanced Industry Standard Architecture (EISA)
• VESA Local Bus (VL-Bus)
• Peripheral Component Interconnect (PCI)
• Accelerated Graphics Port (AGP)
• Universal Serial Bus (USB)
• Small Computer Systems Interface (SCSI)
• FireWire
• Personal Computer Memory Card International
  Association (PCMCIA)

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Industry Standard Architecture (ISA)
An expansion bus commonly used in PCs. It accepts
plug-in boards that control the sound, video
display and other peripherals. Most PCs today
have a combination of ISA and PCI slots however,
many no longer support ISA, and it is expected to
be obsolete by the mid 2000s.Originally called
the "AT bus," it was first used in the IBM AT,
extending the 8-bit bus to 16 bits. Earlier ISA
PCs provided a mix of 8 and 16-bit slots. Today,
PCs have only 16-bit ISA slots.
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Micro Channel Architecture (MCA)

• It was a proprietary 32-bit bus from IBM used in
  PS/2, RS/6000 and certain ES/9370 models. It
  supported 15 levels of bus mastering and
  transferred data from 20 to 80MBytes/sec. The
  boards had a unique, built-in ID that allowed for
  easier installation than ISA devices. In late
  1996, IBM discontinued its use in favor of PCI.

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Enhanced Industry Standard Architecture (EISA)

• EISA was developed in 1988 by a group of nine
  companies including Compaq, Hewlett-Packard, NEC,
  Zenith and others. EISA was developed in response
  to IBM's efforts in developing the MCA bus (Micro
  channel Architecture). EISA was designed to
  increase the capabilities of ISA (hence the
  "enhanced"). With this increase in bus width and
  using an 8.33 MHz clock, the EISA can reach a
  theoretical 33 MB/s transfer rate.

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VESA Local Bus

• (VESA Local-BUS) A peripheral bus from VESA that
  was primarily used in 486s. It provides a
  high-speed data path between the CPU and
  peripherals (video, disk, network, etc.). VL-bus
  is a 32-bit bus that supports bus mastering and
  runs at speeds up to 40MHz. It generally provides
  up to three slots on the motherboard, each slot
  using one 32-bit Micro Channel connector placed
  adjacent to the standard ISA, EISA or Micro
  Channel connector.

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Peripheral Component Interface (PCI)

• PCI was primarily designed by Intel and unveiled
  in 1992. PCI provides a high-speed data path
  between the CPU and peripheral devices (video,
  disk, network, etc.). There are typically three
  or four PCI slots on the motherboard. In a
  Pentium PC, there is generally a mix of PCI and
  ISA slots or PCI and EISA slots. The PCI bus/slot
  has become the industry standard because it
  transmits data at a fast rate and because it is
  simply replacing the older slots such as ISA,
  EISA and MCA. The PCI slot/bus is useable for
  most every type of daughter board except for the
  video cards that are designed for the AGP slot.

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Accelerated Graphics Port (AGP)

• AGP is a relatively new high-speed graphics
  port/bus that was developed by Intel. It provides
  a direct connection between the display adaptor
  and memory. It is designed to handle graphics
  better than the PCI port does such as 3-D
  graphics. It allows the graphics controller to
  directly access main memory and allows 3-D
  textures to be stored in main memory rather than
  video memory. Only 3D video cards connect to the
  AGP slot. The brown AGP slot is slightly shorter
  than the white PCI slot and is located about an
  inch farther back. AGP uses a 32-bit bus. The
  original AGP standard (AGP 1x) provides a data
  transfer rate of 264 Mbytes/sec. AGP 2x is 528
  Mbytes/sec. AGP 4x is 1 Gbytes/sec. AGP 8x is 2
  Gbytes

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Universal Serial Bus (USB)

• The USB bus was introduced in 1996. It is mostly
  used for low-speed peripherals such as the
  keyboard, mouse, printers, scanners and digital
  cameras. It is a unique bus because it doesn't
  connect to daughter boards like the EISA, ISA,
  PCI and AGP slots do and it doesn't connect to
  storage devices like SCSI does. Instead, USB
  ports are connected to your motherboard but is
  external of your tower. USB has a maximum
  bandwidth of 12 Mbits/sec (equivalent to 1.5
  Mbytes/sec), and up to 127 devices can be
  attached to a single USB port.

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FireWire

• The FireWire high-speed serial bus was developed
  by Apple Computer and Texas Instruments. It is
  quite similar to USB as it connects devices to
  your computer. The difference is that FireWire
  can only connect up to 63 devices but is a whole
  lot faster than USB. Also known as the IEEE 1394
  standard, the original spec calls for 100, 200
  and 400 Mbits/sec transfer rates.

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Small Computer Systems Interface (SCSI)
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Personal Computer Memory Card International
Association (PCMCIA)

• Personal Computer Memory Card International
  Association, San Jose, CA. An international
  standards body and trade association that was
  founded in 1989 to establish a standard for
  connecting peripherals to portable computers.
  PCMCIA created the PC Card.