Microsoft Word - TVLSI_4.18_f.docx

Copyright (c) 2014 IEEE. Personal use of this material is permitted. However, permission to use this material for any other purposes must be obtained from the IEEE by sending an email to [email protected]. Abstract—In recent years, memristive technologies, such as resistive RAM (RRAM), have emerged. These technologies are usually considered as replacements to SRAM, DRAM, and Flash. In this paper, a novel digital circuit, the multistate register, is proposed. The multistate register is different than conventional types of memory, and is used to store multiple data bits, where only a single bit is active and the remaining data bits are idle. The active bit is stored within a CMOS flip flop, while the idle bits are stored in an RRAM crossbar co-located with the flip flop. It is demonstrated that additional states require an area overhead of 1.4% per state for a 64 state register. The use of multistate registers as pipeline registers is demonstrated for a novel multithreading architecture – continuous flow multithreading (CFMT), where the total area overhead in the CPU pipeline is only 2.5% for 16 threads as compared to a single thread CMOS pipeline. The use of multistate registers in the CFMT microarchitecture enables higher performance processors (40% average performance improvement) with relatively low energy (6.5% average energy reduction) and area overhead.