the advantages and disadvantages of memory-mapped I/O?

Question

what are the advantages and disadvantages of memory-mapped I/O compared to schemes in which a seperate I/O space is defined? what I/O arrangements can be used with motorola and intel processirs

Answer 1

Memory-mapped I/O (MMIO) and port I/O (also called port-mapped I/O or PMIO) are two complementary methods of performing input/output between the CPU and I/O devices in a computer. Another method is using dedicated I/O processors (channels, used in IBM mainframe computers).



Memory-mapped I/O uses the same bus to address both memory and I/O devices, and the CPU instructions used to read and write to memory are also used in accessing I/O devices. In order to accommodate the I/O devices, areas of CPU addressable space must be reserved for I/O rather than memory. This does not have to be permanent, for example the Commodore 64 could bank switch between its I/O devices and regular memory. The I/O devices monitor the CPU's address bus and respond to any CPU access of their assigned address space, mapping the address to their hardware registers.



Port-mapped I/O uses a special class of CPU instructions specifically for performing I/O. This is generally found on Intel microprocessors, specifically the IN and OUT instructions which can read and write a single byte to an I/O device. I/O devices have a separate address space from general memory, either accomplished by an extra "I/O" pin on the CPU's physical interface, or an entire bus dedicated to I/O





http://en.wikipedia.org/wiki/Memory-mapped_I/O

Answer 2

The advantages you have a wide variety of observations not just your own. The disadvantages you might not like what you learn about yourself of the other person. This suggestion has been brought up many a time and I try my best to place myself in different situations solutions outcomes etc..

Answer 3

what are the advantages and disadvantages of memory mapped i/o