Phoenix: detecting and recovering from permanent processor design bugs with programmable hardware

Although processor design verification consumes ever-increasing resources, many design defects still slip into production silicon. In a few cases, such bugs have caused expensive chip recalls. To truly improve productivity, hardware bugs should be handled like system software ones, with vendors periodically releasing patches to fix hardware in the field. Based on an analysis of serious design defects in current AMD, Intel, IBM, and Motorola processors, this paper proposes and evaluates Phoenix - novel field-programmable on-chip hardware that detects and recovers from design defects. Phoenix taps key logic signals and, based on downloaded defect signatures, combines the signals into conditions that flag defects. On defect detection, Phoenix flushes the pipeline and either retries or invokes a customized recovery handler. Phoenix induces negligible slowdown, while adding only 0.05% area and 0.48% wire overheads. Phoenix detects all the serious defects that are triggered by concurrent control signals. Moreover, it recovers from most of them, and simplifies recovery for the rest. Finally, we present an algorithm to automatically size Phoenix for new processors.