Just a heads up for those using Bumblebee. Primus has come a ways, as has slackware-current.

Using Nvidia 319.49 with the latest bumblebee + primus packages the annoying screen tearing that would crop up at times has been fixed.. hopefully for ever.

Also, the vblank_mode=0 (that used to help this tearing) is no longer needed, and in fact causes screen tearing now... go figure.

If for some reason your build doesn't seem to handle this as expected, feel free to browse my github repo:
https://github.com/WhiteWolf1776/Bumblebee-SlackBuilds

I keep it updated for the latest -current builds for slackware.

Now, back to some lost portal levels

Thanks for the heads-up and the work you do - it's appreciated.