diff --git a/EDAN25-multicore/sammanfattningar/summary_dat11fmu.md b/EDAN25-multicore/sammanfattningar/summary_dat11fmu.md index 24736ee..669b6f6 100644 --- a/EDAN25-multicore/sammanfattningar/summary_dat11fmu.md +++ b/EDAN25-multicore/sammanfattningar/summary_dat11fmu.md @@ -134,12 +134,18 @@ Cache coherence protocols 1. At a write, the cache coherence protocol should either remove all other copies, including the memory copy, or send the newly written data to update each copy. + - The first is called *write invalidate* - - The latter is called *write update protocol*, is almost always better + - The latter is called *write update protocol* + + Which protocol is better depends on the application's sharing behavior, but + in general write invalidation is better. (ref: book pp. 175) + 2. Detecting when a write has completed so that the processor can perform the next memory access + 3. Maintaining illusion of atomicity - with memory in multiple nodes the - accesses can't be atomic, but a SC machine mus behave as if they are. + accesses can't be atomic, but a SC machine must behave as if they are. Memory access penalty ---------------------