Questions about multiple displays

[Matt B]

I have a 23 inch monitor as my main and I have a 15 inch as a secondary. I have two GTX 570's SLI enabled and have the 23 inch connected through and HDMI and the 15 inch connected with VGA. One card is running the 23 inch through HDMI and the other card is running the 15 inch through VGA. Should both monitors be connected to one card or do I have it set up correctly with each monitor on a seperate card? Also in the NVIDIA control panel under manage 3D settings there is an option "Multi-display/mixed-GPU acceleration" under which there is options for Multiple display performance mode, Single display performance mode and Compatibility performance mode. I don't plan on spanning my desktop across or spanning games across on to both monitors. Right now the 15 inch is just acting as a secondary desktop when surfing and having multiple windows/progs open but not games. Is having a secondary monitor slowing down the SLI or vid card(s)?

[Zygomorphic]

Yes, it is slowing down the SLI--SLI is disabled. From what I understand, when in SLI mode, all the monitors must be attached to the head node GPU. Leave the acceleration mode setting alone, just move the second monitor to the first GPU. The spanning across multiple desktops circa Eyefinity is completely optional. If that doesn't improve gaming performance, then it is not an issue either way. In that case, feel free to connect monitors however you like!

[Matt B]

No noticeable performance drop in gaming that I can see as of yet. I usually turn the secondary monitor off while gaming with in mind that maybe having it off won't use any power like if it was on, no idea if that is how it is though. So would the head node GPU be the top most car on the mobo? The one labeled (GTX 570 1) in the Nvidia control panel? Also in the "Configure SLI, Surround, PhysX" setting in the Nvidia control panel the PhysX setting appears to use GTX 570 (1) for the PhysX which the setting is actually on Auto-select allowing Nvidia to choose the best setting. Should this be changed?

[Zygomorphic]

Yes, if the other is labeled GTX 570 2. The lowest number is the master GPU, from what I understand. If the monitor is powered off, then it acts as if it were disconnected, so I don't think it would cause problems. Try disconnecting it physically, if you haven't already, and see if there is any kind of performance change. I would leave the PhysX settings alone, since not everything uses it, and NVIDIA's drivers evaluate the load. If you want a dedicated NVIDIA PhysX card, take a look at getting a third weaker card for that, since PhysX hits the processing power much more than the RAM. I am, unfortunately, not familiar with PhysX or with SLI from experience, I can only tell you what I have read. Maybe someone with more XP can give better advice than I.