Intel 8080

Intel’s 8-bit parallel central processor unit, fabricated on a single LSI chip using n-channel silicon gate MOS technology, became a foundational element in early microcomputer systems and inspired a generation of compatible processors and software ecosystems.

The Intel 8080 was more than an incremental upgrade from the 8008. It was a complete 8-bit parallel CPU designed for general-purpose digital systems, built on Intel’s proprietary n-channel silicon gate MOS process⁴. Marketed as the “Super 8008”³, it replaced the earlier chip’s complex 24-pin package and limited architecture with a refined design and a full 16-bit address bus (A₀–A₁₅), enabling access to 64 KB of memory, a transformative leap at the time. Data moved over an 8-bit bidirectional tri-state bus (D₀–D₇), while control logic relied on six outputs: SYNC, DBIN, WAIT, WR, HLDA, and INTE, and four inputs: READY, HOLD, INT, and RESET⁴. Power delivery required three rails: +12V, +5V, and -5V, alongside ground, and it relied on two-phase clock inputs (φ₁ and φ₂), typical of NMOS designs of the era.

Priced at either $24.95 for the C8080 variant³ or $24.50 for the standard INTEL 8080 CPU¹³, the chip was, in 1976, the sole-source 8080 processor available². This exclusivity, combined with its architectural clarity, made it a magnet for early adopters. The 8080A revision later improved performance with a 1.5 μsec cycle time, down from the original 8080’s 2.0 μsec⁸, though the base clock speed remains undocumented in the source material.

Software development was supported by Intel’s own tools, including FORTRAN80, Version 1.0, which functioned as both an assembler and compiler⁷, and the 8080 Assembly Language Programming Manual (Intel publication #98-004)¹². The broader ecosystem leaned heavily on the Intel 8080 Microcomputer Peripherals User's Manual (Order No. 98-364)¹⁴¹⁵, a document that guided system integrators in connecting memory, I/O, and support chips. The 8080/8085 Assembly Language Programming Manual (Order 98-301) further extended its usability across Intel’s evolving lineup¹⁴¹⁵.

Its cultural imprint exceeded its technical specs. In 1976, both Intel and the fledgling Microsoft embedded the 8080’s identity into their telephone numbers: Intel’s (408) 987-8080 and Microsoft’s (206) 882-8080². This was no coincidence: it signaled alignment with the 8080 as the de facto standard for mainstream computing at the time. The chip became inextricably linked with the CP/M operating system², which used its instruction set to create a widely portable microcomputer OS. Though the documentation does not state CP/M as the official OS for the 8080, their fates were intertwined in practice.

The 8080’s influence radiated through compatibility. The Z80, 8085, and even the 8080 itself were listed among compatible processors in Intel’s literature⁹, with the Z80 ensuring that 8080 codebases could migrate forward. This lineage made the 8080 a pivot point, not because it was the fastest or most elegant, but because it was available, well-documented, and aggressively positioned as a system-building cornerstone.

That said, the surviving documentation is silent on critical details: no release year, no transistor count, no package dimensions, no second-source manufacturers, and no production figures. The gaps are telling. Much of what is commonly attributed to the 8080 (its role in specific machines, its clock speed) rests on external lore, not the primary sources at hand. What remains, however, is clear: the 8080 was a functional, well-supported CPU that Intel positioned as a complete computing engine, not just a logic component. Its design enabled systems that could be programmed, expanded, and standardized, something few earlier processors achieved.

Specifications

References

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8. ACS Newsletter 3 7
9. AUUGN-V05.5
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11. 1981 07 BYTE 06-07 Energy Conservation (1981)
12. 98-129A MDS800 Operator Manual 1975 (1975)
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14. 9800616B iSBC 544 Terminal Controller Hardware Reference Manual Dec78
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16. TheMS-DOSEncyclopedia RayDuncan