In-Pipeline Processor Protection against Soft Errors

Abstract

The shrinking of technology nodes allows higher performance, but susceptibility to soft errors increases. The protection has been implemented mainly by lockstep or hardened process techniques, which results in a lower frequency, a larger area, and higher power consumption. We propose a protection technique that only slightly affects the maximal frequency. The area and power consumption increase are comparable with dual lockstep architectures. A reaction to faults and the ability to recover from them is similar to triple modular redundancy architectures. The novelty lies in applying redundancy into the processor’s pipeline and its separation into two sections. The protection provides fast detection of faults, simple recovery by a flush of the pipeline, and allows a large prediction unit to be unprotected. A proactive component automatically scrubs a register file to prevent fault accumulation. The whole protection scheme can be fully implemented at the register transfer level. We present the protection scheme implemented inside the RISC-V core with the RV32IMC instruction set. Simulations confirm that the protection can handle the injected faults. Synthesis shows that the protection lowers the maximum frequency by only about 3.9%. The area increased by 108% and power consumption by 119%.

Keywords

• processor
• soft error
• functional safety
• RISC-V
• CPU