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ggm8

In this case, processor 1 can just provide processor 0 with the address that it is trying to access, since processor 1 is the home node. Even if we had a red box at index 2 in the directory, but it was in the read state (with the dirty bit off), this would mean processor 2 had accessed this address but had not modified it, so the information would be communicated to processor 0 in this same way. Only when the dirty bit is on, would extra communication from processor 2 be required (e.g. flushing to memory or direct response back to processor 0).

viveksri

Should this be "respond with contents from cache" since the dirty bit is off, therefore the contents are most up-to-date in this processor's cache?

tarabyte

@viveksri I think the slide is correct. Just because the directory owns that piece of memory doesn't mean that the value is in the cache. But because the dirty bit is off, we know the correct value is in memory.