Rage3D 上的討論：

This is released only for the purpose of updating the redistributable function of DirectX8.1 for those who are developers and need to include DirectX. It doesn't change anything as far as features or functions from DirectX8.1a.
after installing DX8.1b, the only NEW(updated) file is msyuv.dll---it's listed as created 6/23/2002. I don't know what it does --- all other files listed in DXDIAG are the same as before.
Thanks! According to what I read, this 8.1b is not really an update at all and explains why some people have downloaded it without seeing a change. What a waste of time.

所以，還是別裝吧。