https://wiki.archlinux.org/index.php/intel_graphics#Disable_Vertical_Synchronization_(VSYNC) Setting my ~/.drirc to:
<driconf>
    <device>
        <application name="Flurry Screensaver" executable="flurry">
          <!--
            Without this flurry screen saver will jump about
            Turn vertical synchronization off:
            -->
          <option name="vblank_mode" value="0"/>
        </application>
    </device>
</driconf> 
As the comment says - this disables vertical synchronization - something to do with using triple buffering on the Intel Driver.
