Requirements, Bottlenecks, and Good Fortune: Agents for Microprocessor Evolution

The first microprocessor, the Intel 4004, showed up in 1971. It contained 2300 transistors and operated at a clock frequency of 108 kHz. Today, 30 years later, the microprocessor contains almost 200 million transistors, operating at a frequency of more than 1 GHz. In five years, those numbers are expected to grow to more than a billion transistors on a single chip, operating at a clock frequency of from 6 to 10 GHz. The evolution of the microprocessor, from where it started in 1971 to where it is today and where it is likely to be in five years, has come about because of several contributing forces. Our position is that this evolution did not just happen, that each step forward came as a result of one of three things, and always within the context of a computer architect making tradeoffs. The three things are: 1) new requirements; 2) bottlenecks; and 3) good fortune. I call them collectively agents for evolution. This article attempts to do three things: describe a basic framework for the field of microprocessors, show some of the important developments that have come along in the 30 years since the arrival of the first microprocessor, and finally, suggest some of the new things you can expect to see in a high-performance microprocessor in the next five years.