2.4 Standard Bus Architectur

      Industry Standard Architecture (ISA)

     .  8 BIT ISA Bus 

         - used in the original IBM PC computers
         -  provides eight data lines and 20 addressing lines,enabling the slot to handle 1m of memory.

      . 16 BIT ISA Bus 

          - IBM introduces the 286 processor in 1984.
          - This processor had a 16-bit data bus,
             - communication between the processor and the motherboard as well would now be 16 bits                      wide.
     

       . 32 BIT ISA BUS 

          - After 32- bit CPUs become available.
          - It was some time before 32-bit bus standards become available

       

          

    

      Micro Channel Architecture (MCA)

        
The MCA bus has some pretty impressive features considering that it was introduced in 1987, a full seven years before the PCI bus made similar features common on the PC. In some ways it was ahead of its time, because back then the ISA bus really wasn't a major performance limiting factor:

• 32 Bit Bus Width: The MCA bus features a full 32 bit bus width, the same width as the VESA and PCI local buses. It had far superior throughput to the ISA bus.
• Bus Mastering: The MCA bus supported bus mastering adapters for greater efficiency, including proper bus arbitration.
• Plug and Play: MCA automatically configured adapter cards, so there was no need to fiddle with jumpers. This was eight years before Windows 95 brought PnP into the mainstream!

       

           - Peripheral Component Interconnect (PCI)

                 
The PCI expansion slot was introduced by Intel, but can be found in both PC's and Macs. It displaced previous computer buses (VESA Local Bus and ISA). PCI was then succeeded by the PCI-E or (PCI Express slot), but PCI is still found in most computers because many expansion devices don't need PCI-E capabilities.

It is also possible to get a PCI card that had more PCI expansion slots on it. This would be helpful for a computer that did not have enough PCI expansion slots for further expansions, although most computers would have an ample amount of slots.