L1 I-cache

By: rwessel (robertwessel.delete@this.yahoo.com), April 1, 2008 12:23 pm
Room: Moderated Discussions
puzzled (anon@yahoo.com) on 4/1/08 wrote:
>Why does Intel always keep the L1 I-cache so tiny? The whitepaper says it remains
>at 32KB in Nehalem. You'd have thought that a larger IL1 could really help branchy
>kernel or database load. IL1 miss even when refill from L2 take ~10 cycles, which pretty much stalls the pipeline.
>Is there a technical reason to keep IL1 small?

In short, you can make a cache fast or big, but not both. Intel has often had rather smaller, but faster L1s than AMD. It's a trade off, yes, you get more misses in the L1 (which are then slower), but all the hits are faster. Depending on which side of that split your workload lands on, that tradeoff may be good or bad for performance.
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