postal2mpdemo - segfaults
wolfenstein - segfaults
ut2003demo - segfaults
ssamtse - works! mostly. Getting segfaults if I change too much from the defaults. Haven't nailed down exactly where yet.
And of course: tuxkart 32bit version works perfectly.
Switching to my singlehead 1024x768 xf86config I'm getting 1700-1750 glxgearmarks on both 64 and 32 bit versions. Not sure if the segfaults are because of the 4496-x86 <-> 4499-AMD64 mismatch or (quite likely) the default installed x11-32bit compatible libs not getting along with my recompiled x11-64bit environment. I'll have to try recompiling X11-32bit next.