slowdown in ImageMagick 6.3.3 03/06/07 Q16

Hello,

Since today I'm experimenting ImageMagick 6.3.3,
I fund a slow down against ImageMagick 6.2.8

Test image :
 identify test.tiff 
test.tiff[0] TIFF 256x256 256x256+0+0 DirectClass 8-bit 1.29831mb 0.180u 0:02
test.tiff[1] TIFF 256x256 256x256+0+0 DirectClass 8-bit 1.29831mb 0.180u 0:02
...
test.tiff[41] TIFF 256x256 256x256+0+0 DirectClass 8-bit 1.29831mb 
test.tiff[42] TIFF 256x256 256x256+0+0 DirectClass 8-bit 1.29831mb 
test.tiff[43] TIFF 256x256 256x256+0+0 DirectClass 8-bit 1.29831mb 

Version: ImageMagick 6.3.3 03/06/07 Q16 :
$ time convert test.tiff test.gif 

real    0m9.493s
user    0m9.005s
sys     0m0.272s

Version: ImageMagick 6.2.8 08/15/06 Q16 :
$ time convert test.tiff test.gif 

real    0m0.402s
user    0m0.240s
sys     0m0.084s

ps 
I'm using the imagemagick package from the slackware distribution.

Thanks