http://gem5.org/Main_Page http://gem5.org/Main_Page Is an open source CPU simulator. I used it in undergrad to run benchmarks with different cache sizes and ca

http://gem5.org/Main_Page http://gem5.org/Main_Page Is an open source CPU simulator. I used it in undergrad to run benchmarks with different cache sizes and cache coherence strategies to see which were more effective. I'm sure Intel and AMD have much more advanced simulation tools though. Most likely multiple, or at least multiple levels of granularity (so you could do stuff like, simulate these potential branch predictor designs at a gate level, and then turn around and simulate the entire CPU at a higher level of abstraction.)