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Reconfigurable computing frameworks such as field programmable gate array (FPGA) provide flexibility to map arbitrary applications. However, their intrinsic flexibility comes at the cost of significantly worse performance and power dissipation than their custom counterparts. Existing design solutions such as voltage scaling and multi-threshold assignment typically trade off energy for performance or vise versa. In this paper, we show that an integrated circuit-architecture-software co-design approach can be extremely effective to simultaneously improve the power and performance of a reconfigurable hardware framework, leading to large improvement in energy-delay product (EDP). First, we select a spatio-temporal reconfigurable computing architecture based on 2-threshold assignment-D memory-array. Applications are mapped to memory as multiple-input multiple-output lookup tables (LUTs) and are evaluated in temporal manner inside a computing element. Multiple such computing elements communicate spatially through programmable interconnects. Next, we exploit the read-dominant memory access pattern in reconfigurable hardware to design an asymmetric memory cell, which provides higher read performance and lower read power leading to improvement in the overall EDP during operation. We note that the proposed memory cell is also asymmetric in terms of its content, providing better read power for one of the logic states (logic “0” or “1”). Based on this observation, next we propose a content-aware application mapping approach, which tries to maximize the logic “0” or logic “1” content in the lookup tables. A design flow is presented to incorporate the proposed architecture, asymmetric memory cell design and content-aware mapping. We show that for both nanoscale complementary metal-oxide-semiconductor (CMOS) [static random access memory (SRAM)] as well as emerging non-CMOS [spin torque transfer random access memory (- TTRAM)] memory technologies, such a co-design solution can achieve significant improvement in system EDP over a conventional FPGA framework.
Emerging and Selected Topics in Circuits and Systems, IEEE Journal on (Volume:1 , Issue: 3 )
Date of Publication: Sept. 2011