Data Buses
 Industry Standard Architecture (ISA) 
       - based on IBM PC/AT
       - recent developments :Plug and Play
Popular for low speed devices

 EISA (Extended Industry Standard Architecture )
       - once popular for servers

 PCI Peripheral computer Interface
         The new standard

PCMCIA Personal Computer Memory Card international Association
        It is a group to promote credit card size memory or I/O device that 
would fit into a personal computer
        - used primarily in laptops and other compact systems

Linux supports ISA, PCI, EISA and PCMCIA bus architectures. Through these
 buses, the system controls and interacts with peripherals.

The CPU uses the following system resources to communicate with the following 
peripherals
 Interrupts (IRQs)
 Input/Output addresses (I/O addr)
 Direct Memory Access Channels (DMA)

An excellent website to help your understanding of various PC design issues,
 limitations, history and overall operation is 
http://www.PCGuide.com

An IRQ is used to signal the processor that a device requires attention. IRQ 
can be shared by devices. For example, a network interface and a disk controller
can reside on the same card and share an IRQ. 

DMA Direct memory access channels used rto improve overall system perfomance 
by allowing the I/O devices to transfer data to/from memory directly ( without the intervention of the CPU).