Fast Company:

The status quo changed in 1971, when Intel announced its 4004 microprocessor. On a single chip the size of a pinky fingernail, it contained the computing functionality of what would have once required multiple circuit boards full of electronics. The 4004 was followed by the 8008 in 1972 and the 8080 in 1974, each one adding dramatic leaps in capability over its predecessor.

And this:

At the heart of the system, the pair initially chose the Intel 8008, an 8-bit CPU. Around that, Kirschner built a device that could generate a 128-by-64 black-and-white display that used a pricey eight kilobits of RAM to store the image of the bitmap (the state of the screen’s pixels).

“At the time, memory was very, very expensive,” recalls Haskel. “I mean, a penny a bit, or something like that.” That limited both the graphical capability of the system and the complexity of the software. Each game had to be less than two kilobits (or 256 bytes) in size. For comparison, this paragraph of text alone takes about 384 bytes to store electronically in its simplest form.

A fascinating read, well written and rich in tech history.