The Gigatron TTL microcomputer is a minimalistic retro computer. It is special in its own oddball way, because it has absolutely no complex logic chips in it, not even a microprocessor! Instead, its CPU is built out of a handful of classic 7400-series chips, also known as the TTL logic series. In the Gigatron these simple ICs not only form a CPU, but this CPU in turn also performs tasks that normally need dedicated peripheral chips. Despite its simple and compact design, the Gigatron works as an 8-bit single-board microcomputer that you can play video games with.

source: solar