Detecting hardware faults with systematic and design diversity: Experimental results

This paper suggests the combined utilization of so-called systematic diversity and design diversity in a time-redundant so-called Virtual Duplex System instead of the structural redundant Duplex System. For this purpose, two diversly designed and systematically transformed variants of an application program are executed sequentially on the same processor. We investigate the safety of Virtual Duplex Systems and propose software diversity techniques (i.e. systematic diversity) to detect hardware faults. Transient faults are detected through the time redundancy and permanent faults by the new software diversity approach. In addition, software design faults and even compiler, library, operating system and underlying hardware design faults can be detected. As an example the systematic diversity techniques 'register permutation' and 'compiler diversity' are applied and evaluated by fault injection experiments. The results show that most hardware faults are detected and that the combined application of systematic diversity techniques and design diversity is very promising for designing fail-silent nodes.