5. MOS Technology 6502 (1975)
Breakthrough application: Apple II (1977)
The 6502 was inexpensive and capable: While the Intel 8080 sold for $149, the 6502 sold for only $25. Many computer hobbyists, including a young man named Steve Wozniak, noticed the inexpensive yet powerful chip and began designing computers around it. One of Wozniak's designs became the Apple II, a PC that sold millions of units and set the tone for late-1970s personal computing.
The 6502 powered many other home computers and video game consoles of the early 1980s; derivatives of the 6502 lay at the heart of both the Atari 2600 and the Nintendo Entertainment System, which makes the 6502 the most influential processor in video gaming.
Photos: Steven Stengel