The use of multi‐chip modules (MCM) and/or multi‐socket boards is the most suitable approach to increase the computation density of servers while keep chip yield attained. This article introduces a new coherence protocol suitable, in terms of complexity and scalability, for this class of systems. The proposal uses two complementary ideas: (1) A mechanism that dissociates complexity from performance by means of colored‐token counting, (2) A construct that optimizes performance and cost by means of two functionally symmetrical structures working in the last level cache of each chip and each memory controller. The coordinated work of both structures minimizes the coherence‐related effects on the average memory latency perceived by the processor. Our proposal is able to improve on the performance of a HyperTransport‐like coherence protocol by from 25% to 60%.

中文翻译：

---

Rainbow：多芯片服务器的可组合一致性协议

使用多芯片模块 (MCM) 和/或多插槽板是提高服务器计算密度同时保持芯片良率的最合适方法。本文介绍了一种在复杂性和可扩展性方面适用于此类系统的新一致性协议。该提案使用了两个互补的想法：（1）一种通过彩色令牌计数将复杂性与性能分离的机制，（2）一种通过在每个缓存的最后一级缓存中工作的两个功能对称结构来优化性能和成本的构造。芯片和每个内存控制器。两种结构的协调工作最大限度地减少了对处理器感知的平均内存延迟的一致性相关影响。