I'm not sure how much I believe that rumor, Mario 64 framerate in R12 would drop below 20 a lot of the time during levels, sometimes as low as 15. So if it was constantly running at full speed in R13 it would require a 100% speedup, or even if it was just full speed "most" of the time it would still need a speedup of 50-60 % at least. That isn't in line with what Strmn wrote on his blog (I believe he said 25-35% speedup in most titles).