| 50 Years Of the Intel 8080 |
| Written by Harry Fairhead | |||
| Sunday, 05 January 2025 | |||
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The Intel 8080 was the very first multi-purpose microprocessor and as such played a pivotal role in the evolution of personal computing. 2024 was the 50th anniversary of the chip that influenced the development of the x86 architecture. The story of how Robert Noyce and Gordon Moore co-founded Intel in 1968 is told in detail in The Road to Silicon Valley, Intel - The Microprocessor Revolution and other articles in IProgrammer's History section. By 1974, Intel was firmly established as the most important manufacturer of microprocessors, having launched the groundbreaking 4004 three years earlier, see Birth of the Intel 4004 - the First Microprocessor.
The 4-bit 4004 and its 8-bit counterpart the 8008, both designed by Federico Faggin, were intended for specific hardware -Busicom’s 141-PF printing calculator for the former and Computer Terminal Corporation’s Datapoint 2200 programmable terminal for the latter. However growing interest in microcomputers and the potential for new applications led to customer demand for a more powerful and versatile microprocessor. Although Faggin came up with the concept of the 8080 in 1971 and proposed the chip to Intel's management in the spring of 1972, Intel didn't immediately approve the project as it wanted to focus on shipping to 4004 and 8008. Once given approval, Faggin hired Masatoshi Shima, who had helped design the logic of the 4004 with him, from Japan in November 1972. Arriving in Silicon Valley from Japan, Shima did the detailed design under Faggin's direction, using the design methodology for random logic with silicon gate that Faggin had created for the 4000 family and the 8008. Much of the development effort was spent trying to integrate the functionalities of the 8008's supplemental chips into a single package in order for it to function as a general-purpose microprocessor. It was decided early in development that the 8080 was not to be binary-compatible with the 8008, instead opting for source compatibility once run through a transpiler, to allow new software to not be subject to the same restrictions as the 8008. For the same reason, as well as to expand the capabilities of stack-based routines and interrupts, the stack was moved to external memory. Another design decision was that the 8080's registers would be specialized, with register pairs having a different set of uses. This also allowed the engineers to more effectively use transistors for other purposes. The Intel 8080 was an eight-bit processor with a 16-bit address bus, enabling it to access up to 64 KB of memory. It operated at a 2-MHz clock speed, though faster variants like the 3.125-MHz 8080A-1 were later released. Its design included seven general-purpose eight-bit registers, a 16-bit stack pointer, and a 16-bit program counter. Its instruction set featured over 70 operations for data transfer, arithmetic, logic, and control flow.
This Intel infographic shows how it stacks up against Intel's latest generation of microprocessor:
The 8080's capabilities made it the ideal choice for early personal computers. It was used for the iconic Altair 8800, sparking the microcomputer revolution and paving the way for the personal computers we know today. Its design influenced the development of the x86 and X64 architecture. Of course there are those who would wish that a different processor, the 6800, would have been the foundation on which the future was built - but it was not to be.
More Information50 Years Ago: Celebrating the Influential Intel 8080 Related ArticleIntel - The Microprocessor Revolution 50th Anniversary of First Microprocessor Birth of the Intel 4004 - the First Microprocessor To be informed about new articles on I Programmer, sign up for our weekly newsletter, subscribe to the RSS feed and follow us on Twitter, Facebook or Linkedin. 
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| Last Updated ( Sunday, 05 January 2025 ) |
