Automatic generation of critical-path tests for a partial-scan microprocessor

We present our experiences generating scan-based critical-path tests for the partial-scan Alpha 21364 microprocessor, including the effects of crosstalk and multiple-inputs switching on path delay. Insufficient scan penetration made this difficult[l], but a new ATPG algorithm increased our coverage. Comparison with actual silicon shows interesting results; we explain them with statistical analysis, factoring the effect of statistical process variation into the effects of crosstalk and multiple-input switching on delay. Finally, we draw conclusions about how to help make future designs amenable to speed testing.