AFAIK CPU speeds are mainly limited by speed of light already today. There is tradeoff between time to fetch data from L1 cache (or register file), and their si

AFAIK CPU speeds are mainly limited by speed of light already today. There is tradeoff between time to fetch data from L1 cache (or register file), and their size. If you want to fetch the data faster, the cache has to be smaller (or the pipeline will stall), because the signal won't propagate fast enough to the cache. But smaller L1 cache also has negative performance impact, because more data has to be refetched from deeper caches.