Multiple Channels, 1 PC - GPU limited?

[jpinheir]

I am working on a three-screen configuration for my sim setup, ideally with two side screens angled in with separate camera views to minimize distortion. My priority is highly framerate-focused - texture/scenery quality and special effects are unimportant. My system can run one stretched camera view (5854x1080 total resolution) very nicely at 60 Hz, and NVidia's GPU utilization chart shows a very stable load. When configured for three channels at the same total resolution, performance bogs down considerably, and the GPU chart bounces around quite a bit between ~100% and much lower values (30-40%). Overall framerate is still generally at/near 60 Hz but there are frequent pauses / lag spikes.

I'm looking into getting a much faster graphics card (new GTX 960 or 1080 to replace my existing NVidia Quadro 4200), but I'm wondering if this would actually make much difference in a 3-channel configuration, or are there processor or memory/PCIe bandwidth limitations that are the bottleneck instead?

- Jacob

[Beau Hollis]

It's difficult to say given that every use case is a bit different. Running extra views does tax the CPU harder. Resource/PCI buss shouldn't be hit too much harder since you still using a single GPU and only one copy of your vertex buffers and textures needs to be copied to one card. One thing you may want to do is tweak your settings and resolution to make more of an isolated test case.
Do this will cut back on the GPU load:
- Shrink all 3 windows down to a smaller size (1/4 the screen for example)
- Disable Volume Fog
- Turn of MSAA
- Turn off HDR
- Reduce shadow texture quality

If things get more stable doing this with 3 views, then a higher end GPU will likely help.

Another thing you might try is doing your 3 views as docked windows with the main 3d window set to panel only. This can rule out issues with float windows such as OS overhead from overlapping windows or issues where the main app window loses focus and dx clocks p3d down as a result.

[jpinheir]

Thanks, great info! I'll try out your suggestions.

- Jacob