•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)