Multiple instruction sets architecture (MISA)

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In the computer hardware industry, there are currently two highly successful instruction set architectures (ISAs): the CISC X86 ISA which is an established standard architecture in the personal computer and server markets, and the RISC ARM ISA which is currently used in many ultra-mobile computing devices, such as smart-phones and tablets. Platforms that run one standard ISA cannot run the other ISA application binaries without recompiling the source code. We are investigating the technical feasibility of designing an energy-efficient multiple instruction sets architecture (MISA) processor that can run both X86 and ARM binaries. We propose an approach in which special decoders interpret the binary instructions of the running ISA and translates them to a native target machine ISA that executes within the processor pipeline. We discuss the completed initial stage of our work involving the design of XAM, an X86 hardware binary interpreter for a MISA processor that runs native ARM instructions, and describe our design in detail. We present performance and energy simulation results of our MISA processor design for a set of synthetic benchmarks including Dhrystone 2.1, measured using the ARM SimpleScalar microarchitecture and power simulator. We also discuss design issues of an ARM to X86 hardware interpreter we are currently developing. We expect the completed X86-to-ARM design and the current ARM-to-X86 work to lay a foundation for designing a well optimized processor having a new native ISA that can run efficiently both X86 and ARM binaries, using direct hardware interpretation.