The field of Evolvable Hardware, applying artificial evolution to the design of digital and analogue hardware is around ten years old. However, the field is far from reaching main stream electronics, although some few examples exist. One cause may be that the problems that are addressed in the field are, in general but not always, relatively simple designs which may be regarded as "toy problems", this work being no exception.

Interest in the possibilities inherent in evolved designs is growing, as may be seen from the inclusion of evolvable hardware as a topic in a number of more traditional electronics conferences. However, how good are the designs that are evolved? How can they be compared to their traditional counterparts? Suitable metrics are needed which enable comparison between these two fields of design and that can provide an accurate and fair evaluation of the given design technique. In this work the issue of fault tolerance is addressed together with the design metric reliability.