Extensive hardware tests and checks cannot solve a problem in a product that is not designed properly. It is not suitable to make a hardware design that appears good and then deem that all facets of the design are OK simply by testing and characteristics. There are a certain number of characteristics that must be designed in from the beginning. Metastability is one of them!! I have seen many products that "worked" but had obsucre problems. Sometimes those obscure problems had to be corrected and almost every time it is traced back to a design problem, often one of metastability that was not considered in the original design or one of some part of the design running outside the specification range.

Michael Karas