Scalable Hybrid Cache Coherence Using Emerging Links for Chiplet Architectures

Multi-die or chiplet architectures provide the most prominent solution to overcome the manufacturing constraints of conventional monolithic-chip architectures and enable scalability to large core counts. However, communication across the chiplets, especially inter-chiplet coherence poses major challenge for high-performance many core applications. To enable scalable coherence in chiplet architectures, we propose novel hybrid snoopy-over-directory coherence enabled through emerging broadcast-capable links with local directory for intra-chiplet coherence and global snoopy for coherence between chiplets. Evaluations show that it improves runtime by $2.8\times$, while requiring 90% and 60% lower storage and energy respectively as compared to hierarchical directory protocol.