This thing has been driving me nuts for a while and I decided to get to the bottom of it this morning. Problem is I'm seeing periodic fps fluctuations with my triplehead2go projection setup.
I cut it down to the patch below. The red context is what displays via the triplehead, the green is monitoring on a regular lcd display. I estimate this is not triplehead specific and the window pos and size parameters can be changed for a regular external monitor.
I have both the monitor and the triplehead set at 60hz refresh rate. I'd expect that by turning sync on on both windows I'd get clean 60 fps. But I don't, see graph in the screenshot.
I've played with sync, floating and other parameters. Sometimes it disappears and stays steady at 60fps but never consistent and repeatable.
What I did find out is that if I set the triplehead to 75hz refresh and turn off sync the oscillation goes away. The monitor only does 50 or 60hz so I leave it at 60.
Is this expected behavior?
I'm on a hackintosh i7-2600k CPU, XFX Radeon HD6870 2GB GPU, OSX Lion 10.7.2, Max 6.0.4. Using HDMI for the monitor, DVI for the triplehead.