From what I hear, many mobos allow you to set the CPU multi at 21x. With the proper BIOS (I forget which version the P6T Deluxe BIOS started supporting it), all you do is set the multi to 21x in the exact same manner as you would to set it to 18x or 19x. It disables Turbo, since it is basically forcing the i7 to run in Turbo mode all the time.
Also according to some of the guys at XS, many of those boards also allow you to turn off the additional Turbo throttling. Unfortunately, this is not possible on the P6T series without the use of a specially modified BIOS for the Deluxe. According to the ASUS rep who provided the BIOS for XS, the in-BIOS option for disabling Turbo throttling is a feature exclusive to their "premium" boards, such as the Rampage II Extreme.
From all I have read over there, the Turbo throttling occurs on the P6Ts under relatively high temps or while using around 1.4 Vcore. My own starts to throttle back very slightly (<0.2 multi) once one of the cores reaches around 84-85C. The throttling tends to be slight, but it is enough that it can cause instability. If I were on watercooling with this chip, it wouldn't be a problem because I can get away with using low voltage.
But anyway, yes, it is a 21x multi that can be set as such in the BIOS, and from what I hear you can turn off all throttling on certain boards.