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.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.)