• Bus Lines
• Expansion Cards
• Cables & Connectors

Bus Lines

Bus Lines are the data pathways that connects the various system components including RAM, CPU, and Expansion Cards.

Two principal bus architectures are:

• Industry Standard Architecture (ISA)   is an 8 or 16-bit bus used by slow older system.
• Peripheral Component Interconnect (PCI) is a high-speed 32 or 64-bit bus widely in use today.

Expansion Cards

Expansion slots provide an open architecture that allow a computer system to expand by connecting it to addition I/O devices thru expansion cards.

 Examples of widely used expansion cards:

• Network Adapter Cards are used to connect computers in a local area network.
   
• Small Computer Interface Card (SCSI) provide a high-speed interface for transferring data to peripheral devices such as disk drives, magnetic tape backup units, scanners, and optical drives.  SCSI devices can be linked together in a daisy chain allowing up to seven devices to be connected to the same port.
    
     
• Television Boards these video capture cards contain also a TV tuner and video converter that changes the TV signal into one that can be displayed on your monitor.
  
• PC cards know by PCMCIA (Personal Computer Memory Card International Association)  are credit-card size expansion cards that are used mainly by portable computers.  Examples of PCMCIA cards are memory, modem, video-adapter, SD-ROM adapter, and external drives adaptors.

Cables & Connectors

Cables are used to connect peripheral devices to expansion cards thru an expansion port.  The expansion port itself is contained on an expansion card that plugs into the motherboard thru an expansion slot.

There are four common port types:

• Serial or RS-232 port allow transmission of data one bit at a time on a single line.  Serial lines are used to link to equipments not near by.  They are used principally for communications, modems, and mice.
    
• Parallel ports  are used for multi-bit data transmission, allowing 8 bits to be transmitted simultaneously, like cars on eight-lanes highway.  These are faster than serial ports but the cable length must be less than 15 feet.
     
• USB (universal serial bus) are expected to gradually replace serial and parallel ports.  They are faster and one USB port can be connected to up to 127 peripheral devices in daisy-chain.
    
• FireWire ports are the newest type.  They are faster than USB ports and can be used to connect high-speed printers and video cameras to the system unit.
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The following table illustrate the different types of cables and connectors used to connect peripheral devices to expansion cards.

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