Joe, Re: "Why in the world would L2 run at the full speed, and Trace cache at full speed? Trace cache is performance critical, smaller, used all the time, L2 is less performance critical, large die area, and is used only on L1 / Trace cache misses? It doesn't pass the common sense test."
You are probably right about the caches. In terms of logical units, the caches are not performance critical - they have a latency. Therefore, if it makes it easier to implement the slower clock, Intel probably did so. Even the fastest caches in the Pentium 4, the L1 data and traces caches, both operate at a 2-cycle latency, so it doesn't make sense to use a full speed clock.
Slightly off topic, but I wonder at which speed the Athlon's caches run at. The Athlon L1 caches both have a 4-cycle latency, so do they run at 1/4th the clock frequency?
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