Application of fast SOCP based statistical sizing in the microprocessor design flow.

ABSTRACTIn this paper we have applied statistical sizing in an industrial setting. Efficient implementation of the statistical sizing algorithm is achieved by utilizing a dedicated interior-point solution method. The new solution method is capable of solving a robust linear program, that is mapped onto a second-order conic program, an order of magnitude faster than the previously explored formulation. Our sizing algorithm is unique in that it represents variability in circuit delay analytically by formulating a robust linear program. The algorithm allows efficient and superior area minimization under statistically formulated timing yield constraints. In this paper, we also report the first use of statistical gate sizing in an industrial microprocessor design flow as a post-synthesis optimization step. Statistical delay models were generated for a 90nm CMOS standard cell library used in the design of an industrial low-power 32bit x86 microprocessor and practical issues related to iterative convergence were explored. When compared to the deterministic sizing, the area savings are 26% for the microprocessor module. The runtime of the algorithm is very low compared to existing statistical sizing methods, achieving an almost 15X speed-up, and scales as O(N1.5), where N is the circuit size.