https://bugs.freedesktop.org/show_bug.cgi?id=52560
--- Comment #1 from Chi-Thanh Christopher Nguyen chithanh@gentoo.org 2012-07-28 14:17:05 PDT --- xorg-server is not responsible for 3D acceleration, mesa is. Xorg.0.log and the output of
LIBGL_DEBUG=verbose glxinfo
might give some hints what is wrong. My guess is that your version of mesa no longer ships the dri1 parts which are needed for 3dfx cards.