Input output port space The 8080 supports up to 256 input/output (I/O) ports,Note: Some Intel datasheets from the 1970s advertise 512 I/O ports, because they count input and output ports separately. accessed via dedicated I/O instructions taking port addresses as operands. This I/O mapping scheme is regarded as an advantage, as it frees up the processor's limited address space. Many CPU architectures instead use so-called memory-mapped I/O (MMIO), in which a common address space is used for both RAM and peripheral chips. This removes the need for dedicated I/O instructions, although a drawback in such designs may be that special hardware must be used to insert wait states, as peripherals are often slower than memory. However, in some simple 8080 computers, I/O is indeed addressed as if they were memory cells, "memory-mapped", leaving the I/O commands unused. I/O addressing can also sometimes employ the fact that the processor outputs the same 8-bit port address to both the lower and the higher address byte (i.e., would put the address 0505h on the 16-bit address bus). Similar I/O-port schemes are used in the backward-compatible Zilog Z80 and Intel 8085, and the closely related x86 microprocessor families.
input output port space the 8080 supports up to 256 input/output (i/o) portsnote some intel datasheets from the 1970s advertise 512 i/o ports because they count input and output ports separately accessed via dedicated i/o instructions taking port addresses as operands this i/o mapping scheme is regarded as an advantage as it frees up the processor's limited address space many cpu architectures instead use so-called memory-mapped i/o (mmio) in which a common address space is used for both ram and peripheral chips this removes the need for dedicated i/o instructions although a drawback in such designs may be that special hardware must be used to insert wait states as peripherals are often slower than memory however in some simple 8080 computers i/o is indeed addressed as if they were memory cells "memory-mapped" leaving the i/o commands unused i/o addressing can also sometimes employ the fact that the processor outputs the same 8-bit port address to both the lower and the higher address byte (ie would put the address 0505h on the 16-bit address bus) similar i/o-port schemes are used in the backward-compatible zilog z80 and intel 8085 and the closely related x86 microprocessor families