It is caused by the entire stack, from the 3d libraries to ui toolkit to individual apps -- it's not only a matter of magically flipping a switch in the sgx driver (a switch that exists indeed, btw). For example you can do tearfree video on a N900 with the current software set.
Thanks for the info, but would you mind being more specific. Are you saying I can solve this inside something like an xorg.conf file? I'm trying to push the envelope, so I thought if I do things like disable double-buffering in GTK widgets, for example, I can avoid a performance hit. See what I mean? I'm a little lost. Please help this ignorant fool.