The Intel 8080, introduced in April 1974, was an 8-bit microprocessor that established the template for the first wave of personal computers. It was a substantial redesign of Intel’s earlier 8008, offering a wider address bus, more registers, faster execution, and a cleaner instruction set, all on a single chip. Its combination of capability and (eventually) low price made it practical to build a usable general-purpose computer around one microprocessor, which is exactly what happened when MITS chose it for the Altair 8800.
Intel’s own Intel 8080 Microcomputer Systems User’s Manual documents the part in detail. The 8080 used a 16-bit address bus, allowing it to address 65,536 (64K) bytes of memory, a large jump from the 8008’s 16K reach. It provided an accumulator plus six general 8-bit registers (B, C, D, E, H, and L) that could also be paired into three 16-bit register pairs, along with a stack pointer and program counter. The instruction set covered arithmetic, logic, data movement, conditional and unconditional jumps, subroutine call and return using a hardware stack in memory, and input/output to as many as 256 ports.
Unlike the self-contained 8008, the 8080 required support chips to form a working system. The manual describes the surrounding MCS-80 family, including the 8224 clock generator and the 8228 system controller and bus driver, which together produced the two-phase clock and the control signals the processor needed. This three-chip core, plus memory and I/O, was enough to build a complete small computer, and it defined the bus and timing conventions that hobbyist designs adopted.
The 8080’s influence reached far beyond Intel. Gary Kildall wrote the CP/M operating system to run on 8080-based machines, which made CP/M the dominant disk operating system of the late 1970s and created a large library of portable 8-bit software. The Altair version of Microsoft BASIC, the first product Bill Gates and Paul Allen shipped, was written for the 8080. The chip’s register model and instruction set were carried forward and extended in the Zilog Z80 and, conceptually, echoed in Intel’s later 8086, so the 8080 sits at the root of a long architectural lineage.
By making a genuinely useful computer buildable around a single, documented, commercially available processor, the 8080 turned the microprocessor from an embedded-control component into the heart of the personal computer. Its appearance set the stage for the January 1975 Popular Electronics cover story and the explosion of micro-based machines that followed.