To summarize, hierarchical snooping suffers from high latency because the snooping and lookup must be done at multiple levels, and high bandwidth at the interconnect at the root, especially as the number of processors increases.
In the second example, memory scales well and local traffic and latency is reduced, but there is a longer latency to memory which is not local (i.e. in a different cluster), compared to just checking the root interconnect.
To summarize, hierarchical snooping suffers from high latency because the snooping and lookup must be done at multiple levels, and high bandwidth at the interconnect at the root, especially as the number of processors increases.
In the second example, memory scales well and local traffic and latency is reduced, but there is a longer latency to memory which is not local (i.e. in a different cluster), compared to just checking the root interconnect.
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