A CMOS test chip that includes a 1k-transistor self-testing encoder/decoder is verifiably error-free at supply voltages down to 20O mV, achieving 1/625 the power-delay product of standard 5 V CMOS. The maximum error-free operating frequency of this circuit as a function of supply and threshold voltage is reported here and voltage scaling of performance is compared with ring-oscillator data reported earlier. The circuit works even when bodies of transistors are forward-biased relative to sources to induce /spl sim/100mV depletion-mode thresholds.<<ETX>>