Write a note on I/O mapped I/O.

1.Port-mapped I/O often uses a special class of CPU instructions designed specifically for performing I/O, such as the IN and OUT instructions found on microprocessors based on the x86 andx86-64 architectures.

2.These two instructions can copy one, two or four bytes (outb, outw, outl) between the EAX register or one of that register's subdivisions on the CPU and a specified I/O port which is assigned to an I/O device.

3.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.

4.Because the address space for I/O is isolated from that for main memory, this is sometimes referred to as isolated I/O.

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