Well, Petrucci plays (in his Rock Discipline) 208 bpm, four notes/beat = 13,73333.. notes/sec (All played cromaticly, so no repeated tones if you get what I mean..)

He also tries 216 bpm (4 notes/beat) in the same scale and he manage to play it for like 2,5 seconds. That's 14.4 notes/sec

However, I don't think I ever heard something that fast before in my whole life. Perhaps somekind of tremolo, but I suppose it doesn't count in this case..