I have tried to build mplayer on the Snow Leopard(with 64bit kernel OFF) By default, ./configure make will result a 64bit mplayer.(I could tell from the Activity Monitor) and in the configure output, the cpu was recognized as x86_64. (I thought this is the direct reason. Although the output of "arch" is i386, it seams like the default behavior of gcc in this system is to build 64bit bundle) so then I tried to set CFLAGS, LDFLAGS, CXXFLAGS with "-arch i386", then make clean ./configure make this time, in the configure output, the cpu was recognized as i386. But build failed with faults at some places in mp3lib. It said some registers can't be recognized by the assembler, in dct64_MMX.c . (Sorry I didn't have a raw copy of the log right now) Also I have searched around,it seams that other projects met the problems too. http://boomswaggerboom.wordpress.com/ 2009/08/27/building-32-bit-firefox-on-mac-os-x-10-6/ But I saw the warning that mplayer's configure has strongly depend on the CFLAGS. So I am not sure whether the solution mentioned above could work. - Also I found some other sayings(not sure), to set CC="gcc -m32", I have not tried yet. Sorry for the long message, but who could explain how to configure the mplayer32bit under 64bit env?