Modern Microprocessors: A 90 Minute Guide
This is a really good overview of modern processor design.  I keep noticing that a lot of people don't seem to understand the CPU designs past the five stage pipeline taught in undergrad architecture courses and this document does a lot of good work in targeting the areas that folks are most likely to have misconceptions about.<p>I do wish they covered trace caches, or as they're known partly in their more modern form, u-op (micro-op) caches, which are back in modern Intel chips again and cause some interesting performance artifacts.  (The old trace caches of the P4 chips are different than the u-op caches of the new architectures, since the trace cache actually encoded branch predictions into the actual cache line lookup, which was always pretty wild.)