The 4004, which was launched 35 years ago today, was a 4-bit processor containing 2,300 transistors. The current Core 2 Duo range has 291 million transistors.
Intel is making the chip specs and blueprints available on an open licence for non-commercial use, and is allowing some limited commercial licensing.
The chip was originally developed for the Nippon Calculating Machine Corporation for use in calculators, and the company should have kept the rights to the chip's design. Intel offered Nippon a lower price per unit in exchange for the rights.
The 4004 chips are now highly collectable and can change hands for up to US$1,000. Most valuable are the original white and gold chips and those without dates printed on the casing, indicating that they were among the first batches.