A Multi-protocol cache controller

Cache coherence protocols, Bus multiprocessor systems, Tuning characteristics.

Bus-based shared memory multiprocessors with per-processor caches use either invalidation or update protocols to maintain cache coherence. This paper suggests mixing protocols for different data objects within a single application, depending on whatever protocol is more efficient for an access pattern to a given object. The model of a two-protocol cache coherence controller has been created in CSP-based Transim language. Each cache line is tagged not only with the state, but also with the protocol type. Two most frequent 4-state, write-back protocols are implemented: MESI (invalidation) and Dragon (update) protocol. The model will be used for experimental evaluation of the proposed controller, which could then be used for processor cores with primary caches in SoC or for secondary caches in multiprocessors with standard microprocessors.