Mempack: An order of magnitude reduction in the cost, risk, and time for memory compiler certification

Advances in memory compiler technology have helped accelerate the integration of hundreds of unique embedded memory macros in contemporary low-power, high-speed SoCs. The heavy use of compiled memories poses multiple challenges on the characterization, validation, and reliability fronts. This motivates solutions that can reduce overall cost, time, and risk to certify memories through the identification of a reduced set of ‘fundamental’ memory macros that can be used one or more times to realize all memory instances in the design. This paper describes MemPack, a fast, general method based upon the classical change-making algorithm for the identification of such fundamental memory macros. By relaxing the need for exact realization of memories and tolerating wastage within the context of change-making, MemPack enables tradeoffs between memory capacity and reduction in the number of fundamental macros. It also controls multiplexing and instantiation costs, minimizing the impact on critical path delay and address line loading. Results on industrial and synthetic benchmarks for three different optimization objectives (performance, balance, and minimization) show that MemPack is effective in identifying fundamental sets that are as much as 16× smaller than the original set for 0.8–4.7% wasted bits.