Memory mapped I/O vs Port mapped I/O [closed]

问题

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Closed 6 years ago.

Memory mapped I/O is a technique which allows the use of central memory (RAM) to communicate with peripherals. Port mapped I/O uses ports (with special assembly instructions) to communicate over digital ports.

What are the advantages of one method with respect to another?

回答1:

As Cthulhu said,

• memory mapped I/O allows writing/reading to I/O device ports the same as reading/writing to normal memory (using the same machine code/asm)

but there is a disadvantage:

• you use up physical memory address space for your memory mapped I/O devices (think of 32 bit Windows not being able to access all 4G of RAM on a PC)

So an advantage of using the port mapped I/O method is that you have a separate address space for your I/O devices and you can use the whole memory addressing range to access memory.

EDIT: Here is a more complete answer to your question: hardware ports to memory addresses

来源：https://stackoverflow.com/questions/15371953/memory-mapped-i-o-vs-port-mapped-i-o