52 comments Microprocessor and Computer Architecture, Notes

Write the differences between Isolated I/O and Memory Mapped I/O.

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Last updated on June 13th, 2020 at 08:31 pm

Memory Mapped I/O and Isolated I/O are two methods of performing input-output operations between CPU and installed peripherals in the system. Memory mapped I/O uses the same address bus to connect both primary memory and memory of hardware devices. Thus the instruction to address a section or portion or segment of RAM can also be used to address a memory location of a hardware device.

On the other hand, isolated I/O uses separate instruction classes to access primary memory and device memory. In this case, I/O devices have separate address space either by separate I/O pin on CPU or by entire separate bus. As it separates general memory addresses with I/O devices, it is called isolated I/O.


Read More: What are memory mapped I/O and isolated I/O?

Differences Between Isolated I/O and Memory Mapped I/O:


Isolated I/O
No.
Memory Mapped I/O
Isolated I/O uses separate memory space.
01
Memory mapped I/O uses memory from the main memory.
Limited instructions can be used. Those are IN, OUT, INS, OUTS.
02
Any instruction which references to memory can be used.
The addresses for Isolated I/O devices are called ports.
03
Memory mapped I/O devices are treated as memory locations on the memory map.
IORC & IOWC signals expands the circuitry.
04
IORC & IOWC signals has no functions in this case which reduces the circuitry.
Efficient I/O operations due to using separate bus
05
Inefficient I/O operations due to using single bus for data and addressing
Comparatively larger in size
06
Smaller in size
Uses complex internal logic
07
Common internal logic for memory and I/O devices
Slower operations
08
Faster operations

52 comments

  8. I studied these in my 7th semester, 1.5 years back. I can't answer you. These are just my notes those I made at that time, hoping that someone else will help you.

  29. difference u writtrn is quite in the easy language ….i love it….plz add some more difference u know…..that may help us

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