The problem with MESI is that this protocol complements Intel’s older bus-based architecture but not the cc-NUMA system.
In a ccNUMA system, the MESI protocol would send many redundant messages between different nodes, often with unnecessarily high latency. In particular, when a processor requests a cache line that is stored in multiple locations, every location might respond with the data. However, the requesting processor only needs a single copy of the data, so the system is wasting a bit of bandwidth.
The problem with MESI is that this protocol complements Intel’s older bus-based architecture but not the cc-NUMA system.
In a ccNUMA system, the MESI protocol would send many redundant messages between different nodes, often with unnecessarily high latency. In particular, when a processor requests a cache line that is stored in multiple locations, every location might respond with the data. However, the requesting processor only needs a single copy of the data, so the system is wasting a bit of bandwidth.