BROOM: An Open-Source Out-of-Order Processor With Resilient Low-Voltage Operation in 28-nm CMOS

The Berkeley resilient out-of-order machine (BROOM) is a resilient, wide-voltage-range implementation of an open-source out-of-order (OoO) RISC-V processor implemented in an ASIC flow. A 28-nm test-chip contains a BOOM OoO core and a 1-MiB level-2 (L2) cache, enhanced with architectural error tolerance for low-voltage operation. It was implemented by using an agile design methodology, where the initial OoO architecture was transformed to perform well in a high-performance, low-leakage CMOS process, informed by synthesis, place, and route data by using foundry-provided standard-cell library and memory compiler. The two-person-team productivity was improved in part thanks to a number of open-source artifacts: The Chisel hardware construction language, the RISC-V instruction set architecture, the rocket-chip SoC generator, and the open-source BOOM core. The resulting chip, taped out using TSMC’s 28-nm HPM process, runs at 1.0 GHz at 0.9 V, and is able to operate down to 0.47 V.