Geneva: A Dynamic Confluence of Speculative Execution and In-Order Commitment Windows

Modern out-of-order microprocessors are increasingly expanding resources such as reorder buffer (ROB) and instruction queue (IQ) for memory-level parallelism (MLP). While this expansion effectively addresses the memory wall challenge, it also incurs notable cost and energy trade-offs. To tackle this, we propose Geneva, a microarchitecture that improves performance and saves energy. Geneva reallocates a portion of an ROB to serve as a dynamic queue (DQ), used as an ROB, IQ, or both depending on operational needs. Geneva saves energy by 15.6% and improves performance by 2.6% compared to the conventional out-of-order core.