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