Intel 8080

The Intel 8080 was an early microprocessor designed and manufactured by Intel. The 8-bit CPU was released in April 1974 running at 2 MHz, and is generally considered to be the first truly usable microprocessor CPU design. It was used in many early computers, forming the basis for machines running the CP/M operating system (the later, compatible, Zilog Z80 processor would capitalize on this, CP/M becoming the dominant OS of the period much like MS-DOS for the PC a decade later). Shortly after the 8080, the Motorola 6800 competing design was introduced.

The Intel 8080 was the successor to the Intel 8008 (with which it was assembly language source-compatible because it used the same instruction set developed by Computer Terminal Corporation). The 8080's large 40 pin DIP packaging permitted it to provide a 16-bit address bus and an 8-bit data bus. It had seven 8-bit registers (six of which could be combined into three 16-bit registers), a 16-bit stack pointer to memory (replacing the 8008's internal stack), and a 16-bit program counter.

The 8080 had 256 I/O ports (allowing I/O devices to be connected without the need to allocate memory space – as is required for memory mapped devices – but at the expense of separate I/O instructions). The first single-board microcomputer was built on the basis of the 8080.

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