January 2026—OpenXiangShan/CoupledL2 delivered a critical opcode coverage improvement and fixed a decoding bug in the forward path. The changes strengthen correctness and reliability of opcode handling, enabling broader opcode support and more robust downstream integration.

OpenXiangShan/CoupledL2 (Dec 2025) monthly summary: Delivered two high-impact features and implemented code maintenance improvements in TL2CHICoupledL2 and MMIOBridge, with clear traceability to commits. This month focused on performance optimization and maintainability, translating into tangible business value and technical gains across the L2 stack.

November 2025 (OpenXiangShan/CoupledL2) focused on boosting cache coherence, data-path throughput, and decoding correctness in the L2/L1 coupling stack, while introducing timing-conscious pipelines to reduce stalls. The work delivers tangible performance and reliability improvements in the L2 data path, with concrete commits that align with business goals of higher CPU efficiency and stronger hardware correctness.

OpenXiangShan/CoupledL2 (2025-09) monthly summary: Delivered enhanced CHI TestTop logging by embedding CLog.B recording, expanding time-control options, and updating build/test tooling to improve observability and debugging across CHI transactions. This work increases traceability, reduces debugging time, and sets the foundation for deeper performance analysis in CHI pipelines.

Month: 2025-07 — Focused on reliability of the memory subsystem and dependency management for CoupledL2. Delivered a critical AXI4Memory bug fix addressing ID metadata loss under simultaneous AW and WLAST signals, and upgraded the CoupledL2 submodule to a newer commit to incorporate upstream improvements. These changes reduce risk in core memory transactions, improve system stability under bursty workloads, and align with upstream fixes and roadmap priorities. Demonstrates strong concurrency debugging, submodule management, and end-to-end validation capabilities.

June 2025: Focused on improving correctness, reliability, and maintainability across OpenXiangShan's CoupledL2 and XiangShan subsystems. Implemented critical MSHR/NDERR fixes to ensure correct EWA signaling and robust replacement task handling, and upgraded the CoupledL2 submodule to align with upstream changes. These efforts reduce edge-case failures, improve transaction correctness, and simplify future integration with upstream work.

May 2025 highlights for OpenXiangShan/CoupledL2: delivered enhancements to MPAM non-secure attribute handling and fixed cross-module binding consistency, strengthening memory access security and accurate attribute reflection across the MPAM stack.

April 2025: Delivered significant enhancements in logging, simulation time handling, and CI/CD reliability across Utility and CoupledL2. Focus on business value: improved debugging fidelity, time-source accuracy for CHI logs, simpler MSHR code, and more reliable CI for faster feedback and fewer production delays.

March 2025 — OpenXiangShan/CoupledL2: Hardened the memory subsystem with focused MSHR and MainPipe fixes to improve data integrity, coherence, and reliability in nested SnpOnce scenarios. Key features delivered: (1) MSHR correctness and cache-coherence fixes spanning meta handling, SnpOnce nesting, and tag management; (2) MainPipe reliability and data-propagation fixes for nested SnpOnce/SnpOnceFwd, ensuring proper tag propagation and correct data returns across UC/BRANCH states. Major bugs fixed include updated MSHR meta on ProbeAck/ProbeAckData, removal of duplicated retToSrc logic, prevention of directory-tag overwrites on CBOAck, robust UC->SC handling for SnpOnce nesting, and ensuring CMO transactions start after meta writes. Overall impact: higher memory-subsystem correctness, reduced data-corruption risk in nested paths, and improved system reliability and debuggability. Technologies/skills demonstrated: memory-subsystem debugging, MSHR/MainPipe engineering, coherence-protocol understanding, and Chisel/RTL development discipline.

February 2025 monthly summary for OpenXiangShan/CoupledL2 focusing on enhancements to cache coherence in nested snoops and releases, targeted bug fixes, and improved system stability. The work emphasized robust state management, reduced race conditions in MSHR scheduling, and correct arbiter initialization to ensure reliable MMIO and TL2 interactions.

January 2025 - OpenXiangShan/CoupledL2: Delivered core MSHR improvements to strengthen cache coherence, expanded eviction handling, and improved correctness across critical paths. Enhanced testing capabilities with ECC-enabled detection and added CI robustness to preserve artifacts for debugging. These work items advance reliability, debuggability, and overall system resilience in the memory subsystem.

December 2024 monthly summary: Delivered targeted stability improvements and feature updates across OpenXiangShan/CoupledL2 and XiangShan, with a focus on cache coherence, memory attribute handling, and protocol refinements. The work enhanced data integrity, reduced stalls, and improved interoperability with CHI and submodule integration, translating to measurable performance and reliability gains for memory subsystems and CO-mode operations.

OpenXiangShan/CoupledL2 — 2024-11 Monthly Summary This month focused on delivering a more robust memory subsystem for the CoupledL2 engine, aligning CMO data path with TileLink, fortifying MSHR handling, and correcting MMIO write behavior. The work improves data path reliability, reduces stalls, and enhances coherence correctness in production scenarios.

For Oct 2024, OpenXiangShan/CoupledL2 delivered key improvements in DCT handling and CHI TestTop infrastructure, improving cache correctness, test coverage, and maintainability. The Data Cache Target (DCT) opcode forwarding bug was fixed, preventing misused opcodes and cache coherency state errors. CHI TestTop infrastructure was enhanced to support broader test scenarios: expanded TileLink ID ranges for L1 data caches and uncached clients; refactored parameter handling in TestTop_CHIL2; added upwards Cache Coherence Protocol (CMO) testing support. These changes reduce DCT risk, improve test reliability, and enable broader Coherence protocol validation in production-like environments.