Speculative Execution and Timing Predictability in an Open Source RISC-V Core

We present MINOTAuR, a timing predictable open source RISC-V core based on the Ariane core [28]. We first modify Ariane in order to make it timing predictable following the approach used to design the SIC processor [11]. We prove that the instruction parallelism in the Ariane core does not prevent from enforcing timing predictability. We further relax restrictions by enabling a limited amount of speculative execution and we are still able to formally prove that the core is timing predictable. Experimental results show that the performance is reduced by only 10% on average compared to the original Ariane core.