What effects does the X-Parameter really affect?

[Saga Musix]

I didn't find a list on the forums or the wiki, so I'm asking here: Which effects can be extended thru the X-Parameter?
Also, how do you really use it? I tried it together with Txx and Cxx, but I could neither set the tempo to more than 255bpm, nor could I break to a row after row 255.

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ModPlug Tracker  IT
|........#01
|........C12

[Relabsoluness]

From RC1 release notes:

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Parameter extension pattern effect:  New # command, used to extend the parameter values of certain other commands:
Examples:

  Oxx (9xx):
  -------------
  C-5 10 -- O21 (21h = 33)        C-5 10 -- O21
  --- -- -- #02                   --- -- -- #02
                                  --- -- -- #01

  -->OFFSET = 33 * 256 + 2     --> OFFSET =  33 * 65536 + 2 * 256 + 1


  Cxx (Dxx):
  -------------
  C-5 10 -- C01
  --- -- -- #10

  -->PATTERN BREAK line =  1 * 256 + 16

 
  Txx (Fxx):
  -------------
  C-5 10 -- T01
  --- -- -- #02
 
  -->TEMPO = 1 * 256 + 2