We did real production benchmarks using different servers. Servers were put into production behind load-balancers, then weights on load-balancers were changed so we got highest number of dynamic PHP requests per second. It must sustain that number of requests for some time and no drops or request queue were allowed. With static requests numbers for Opteron and T2000 were even better but we are mostly interested in dynamic pages.
Link: milek.blogspot.com
