MMX: pack without saturation?

I have a value like this in mm0:
FFBF FFCF 00DF 00EF

And I want to turn it into this using MMX:
BF CF DF EF (00 00 00 00)
(packing the lower bytes of the words)

Currently I'm using packuswb, but this transforms it into:
00 00 DF EF

Of course I could and mm0 with 00FF 00FF 00FF 00FF before using packuswb, but is there a smarter way of packing the lower bytes of the words without saturation? IMO it's a more simple transformation, but I don't know whether MMX does support it somehow. There is packsswb, but I cannot find an instruction without saturation, just ignoring the higher bytes of the words.

Jens

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Jens Gruschel
http://www.pegtop.net
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