Int 1F Fn FB  U - C&t "superstate" Bios - Get/set Cpu Speed                [b]

   AH = FBh
   BL = function
       00h get CPU speed

       Return: AL = current CPU speed (00h = fast, 01h = slow)
       01h set CPU speed
       AL = new CPU speed (00h = fast, 01h = slow)

See Also: AH=FCh/BL=00h