Member-only story
Intel 8080 — launching the micro-computer revolution
Many herald the Intel 8080 microprocessor, released in 1974, as the chip that launched the microcomputer revolution. True, given that it powered the Altair 8800 and IMSAI 8080, the first computers available to the public.
The 8080 was yet another genius design by Federico Faggin and Masatoshi Shima, the chip designers behind the 4004 and 8008 processors.
In the early 1970s, Intel received considerable interest from around the world from device manufacturers seeking more capable and faster microprocessors. After the success of the 4004, this led Intel’s Faggin to work on a new chip, the 8008, and then the 8080.
Whereas the 8008 was an 8-Bit processor with a 14-bit address bus, Faggin and Shima wanted the 8080 to offer full 16-bit compatibility. They paired 8-Bit registers to offer real 16-bit instructions, and increased the address bus to 16-bit, allowing full access to a massive (at the time) 64Kb of memory. This required the use of a huge 40-pin package compared to the 8008’s 18-pin package, but this larger package simplified usage of the microprocessor for the consumer.
The first 8080 clocked at an impressive 2MHz, four times faster than the 8008. This allowed it to execute several hundred thousand instructions per second, approaching the power of some mini-computers of the day.
It also integrated many of the TTL glue chips that once surrounded the 4004 onto the 8080 itself. Feedback from customers inspired Faggin and Shima to rebuild and improve the interrupt architecture that they deemed inadequate on the 8008. Another complaint had been the tiny call stack built-in to the 8008. To remedy this, the 8080 moved the stack out into memory, addressed by a 16-bit stack pointer register, a technique used by nearly all microprocessors to follow.
