Hi, Looking at the codes for the fetch unit in O3, I realized that the fetch unit does not take advantage of non-blocking i-caches. The fetch unit does not initiate a new i-cache request while it is waiting for the an i-cache response. Since fetch unit in O3 does not pipeline i-cache requests, fetch unit throughput reduces significantly when the i-cache hit latency is more than 1 cycle. I expected that fetch unit should be able to initiate a new i-cache request each cycle (based on BTB addr or next sequential fetch addr) even when fetch unit is waiting for i-cache responses. Any thoughts on this?
I understand a large fetch buffer can mitigate this to some degree... Thanks, Amin
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