The original Intersil, Inc. was founded in 1967 by the Swiss physicist Jean Hoerni to develop digital watch Integrated Circuits (ICs).

[disputed – discuss] The European subsidiary Eurosil was originally partially funded by SSIH, a Swiss watch company.

Later-on, Intersil had a development contract with the Japanese company Daini Seikosha and became supplier of low-voltage CMOS watch ICs for Seiko.

A creation of Intersil (as Harris Semiconductor) is the PRISM line of Wi-Fi hardware: that group of products was sold to GlobespanVirata in 2003, and maintained by Conexant.

The company also completed a series of acquisitions, two of which are still part of the portfolio, Zilker Labs[11] digital power devices and Techwell[12] automotive and security and surveillance products.