Timeline for What are the differences between memory coherence and cache coherence?
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| Jul 11, 2021 at 15:32 | comment | added | pveentjer | Processors do this completely automatic and it is pretty efficient as long as you don't have contention. As long as there is no contention, the CPU can use the cacheline without any form of cache coherence traffic or communication with main memory. | |
| Jul 11, 2021 at 15:30 | comment | added | pveentjer | This information is not correct. Caches are always coherent on modern processors; the only type of processor I know with incoherent caches is a GPU. Apart from that, modern caches are write behind caches, not write through (wt is very inefficient). So in theory, there is no reason for a modified cache line to end up in main memory. There are some limitations on some cache coherence algorithms like MESI whereby a read by a different CPU of a dirty cache line force the cache-line to be flushed to main memory. But MOESI (AMD) resolves that problem. Also when there is a shortage of cache. | |
| Feb 6, 2021 at 17:13 | history | answered | gnasher729 | CC BY-SA 4.0 |