Xinerama disables acceleration. There's been a decade of discussion on this, but no good solutions have been discovered yet. If you want accelerated multi-card

Xinerama disables acceleration. There's been a decade of discussion on this, but no good solutions have been discovered yet. If you want accelerated multi-card X, use one screen per card; this means that you can't move windows between cards. If you want accelerated multi-monitor X on one card, use Xrandr instead of Xinerama.