• Suppose instead of updating remote cache lines, we invalidate them all when a store occurs? • After the first write to a cache line we know there are no remote copies – so subsequent writes don’t lead to communication • Is invalidate always better than update? – Often – But not if the other processors really need the new data as soon as possible • Note that to exploit this, we need a bit on each cache line indicating its sharing state • (analogous to write-back vs write-through)