A small nit that bugs me in the original post > The difference between AES128 and AES256 appears to be approximately 26%, rather than the 40% one might expect

A small nit that bugs me in the original post > The difference between AES128 and AES256 appears to be approximately 26%, rather than the 40% one might expect (AES128 does 10 rounds, AES256 does 14 rounds). There may be some limiting factor that prevents AES128 running at the expected speed, or perhaps this CPU has extra area dedicated to making AES256 faster. The hardware in the CPU performs a single AES round, it does not dedicate more hardware for AES256. One who understands that AES-GCM is not just AES knows that the difference is due to the GCM overhead, that is the same for 128 and 256.