ISBoxer and multiple GPUs

Does ISBoxer utilize the GPU of an additional video card when the video is being displayed on the monitor connected to the extra card? Or is all rendering performed on the primary GPU?

I currently have 2 GTX 570s, and I'm pretty sure I'm hitting a memory bottleneck on my GPUs, as according to the EVGA utility, my vram is maxed at 1.2GB when running 5 wows.

I'm thinking of upgrading to a GTX 6XX series card, with 2+ GB memory, maybe even springing for a 4GB 670.

I have 6 monitors, currently I have them spread accross the 2 570s and the onboard Intel HD Graphics. I can't utilize the Nvidia surround feature, as the resolutions are not the same, so I need a second GPU to handle the the other 2 monitors. If I keep one of the 570s, would that give me better performance than using a POS $20 GPU? Or should I bite the bullet and get matching monitors so I can use the built in functionality of the new GPU?

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Does ISBoxer utilize the GPU of an additional video card when the video is being displayed on the monitor connected to the extra card? Or is all rendering performed on the primary GPU?

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This is discussed under GPU Management. Not surprisingly, even though it is explained 3 different ways on that page, anyone with multiple GPUs still seems to ask the same question.

I'll try to explain it in a different way, maybe this way will work better.

The way GPU utilization works is when your game starts up Direct X, it says to Direct X "I want 3d on this display" (corresponding to a plug on your video card, with a monitor attached). That's one of your monitors. If the game window is moved away from that display, either by you dragging the window, ISBoxer moving the window, etc, there may be a significant performance penalty for doing so. On Windows XP, there is definitely a performance penalty for doing so, but on Vista or later, as long as it's staying on the same Video Card, there should not be a performance penalty.

ISBoxer will enforce each game instance's selected display, based on your Window Layout. For any Slot that has a Home Region in your Window Layout, the display with its Home Region on it will be the bound display/GPU. For any Slot that doesn't have a Home Region, the display with the Active Region on it will be the bound display/GPU.

I'll run through a couple examples to illustrate...

So... say you have 2 characters on 2 monitors that are plugged into 2 different GPUs. And you have a Swapping layout, so that your windows switch spots between the 2 monitors. There's a few ways to do this Window Layout, but typically you'd have 2 Regions with one Active on the main screen and the second Slot's Home Region on the second screen, and Slot 1 has no Home Region. (This makes it "Roaming" and it will borrow a Slot from whichever moves to the Active Region.) So following the above logic, Slot 1 would be bound to the primary display, and Slot 2 would be bound to the secondary display. Allowing these windows to swap positions is guaranteed to incur a significant performance hit on any version of Windows. (If they were on the same video card, the performance hit would only exist on Windows XP, but not Vista or later.)

Now with the same 2 characters, monitors and GPUs as above, let's pretend instead of having Slot 1 not have a Home Region and borrowing Slot 2's Region, we make 3 Regions in the Window Layout. We have the Active Region on screen 1, and 2 Home Regions on screen 2. Now, since both are assigned a Home Region, and both of the Home Regions are on screen 2, both game instances will be assigned to the second GPU, and the moment one of them moves to the Active Region, it is guaranteed to incur a significant performance hit on any version of Windows. (If they were on the same video card, the performance hit would only exist on Windows XP, but not Vista or later.)

This is why the Window Layout Wizard includes a "cross-monitor swapping" option you can set to False. By setting that to false, you guarantee that the generated Window Layout will not move a window from one monitor to another (it will keep your Active Region on the same screen as the Home Regions, and may split into multiple Swap Groups). This guarantees that you can't run into the described performance hit with multiple GPUs, without having to actually understand what I'm talking about. ;)



Finally, if you want to double-check which display is being assigned to any given game instance, set the "in-game Inner Space console hotkey" option in your Character Set, and press it in a newly-launched game instance. Somewhere in the Console will be a line that says in teal, "Window Layout binding to monitor: <...>" where the <...> is probably like "\\.\DISPLAY1" as should correspond to what is shown in your Window Layout (or the Window Layout Wizard).