RC-3 Relay Computer

RC-3 at Goodwill

RC-3 at the Goodwill Computer Museum

The RC-3 is an 8-bit computer with a 16-bit address bus that uses 418 electromechanical relays as logic elements.  It has 421 lights and 134 switches on its front panel, and runs at the blinding speed of 6 Hz.  It was designed and built by the founders of the Museum of Computer Culture during the 2010-2011 timeframe, when they were volunteers at Goodwill Computer Museum.  This article describes in the following pages the design and construction of this machine.

RC-3 is based on the design of a relay computer constructed by Dr. Harry Porter at Portland State University.  Documentation for his machine is available at

Complete documentation for RC-3 is available on this site at

In particular, these files may be of interest:

You can see (and hear!) the RC-3 in operation below…