CSEE 6861 CAD of Digital Systems Handout Lecture 14 4 28 16 Prof Steven M Nowick nowick cs columbia edu Columbia University New York NY USA Department of Computer Science and Elect Eng Introduction to Approximate Computing follows Handout 43 paper 1 Full Adder Designs Mirror Adder MA Conventional Mirror Adder efficient transistor level design Figures courtesy of V Gupta D Mohapatra S P Park A Raghunathan and K Roy IMPACT IMPrecise adders for low power Approximate CompuTing Proceedings of the IEEE Int Symp on Low Power Electronics and Design 2011 Full Adder Designs Mirror Adder MA Simplified Approximate Mirror Adders 3 4 2 Full Adder Designs Mirror Adder MA Simplified Approximate Mirror Adders Layouts Full Adder Designs Mirror Adder MA Accurate Approximate Mirror Adders Truth Table 5 6 3 Full Adder Designs Mirror Adder MA DSP Application areas Discrete Cosine Transform DCT and Inverse DCT IDCT Approximate Mirror Adders Output quality for 7 9 LSB bits using approximation peak signal to noise ratio PSNR accurate 20 bit adder PSNR 31 16dB Full Adder Designs Mirror Adder MA DSP Application areas DCT and IDCT Goal use improved performance to reduce Vdd for power savings 7 8 4 Full Adder Designs Mirror Adder MA DSP Application areas DCT and IDCT power and area savings Full Adder Designs Mirror Adder MA DSP Application areas DCT and IDCT overall quality metric for approximate designs 9 10 5