2 Geforce, 5 Screen Configuration (non SLI) - Win7

JustinSch

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Jun 19, 2015
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Hi,

We have a requirement for a simulator that requires 5 screens for the out of window display. We had hoped to achieve this with two Geforce GTX 970s in non-SLI configuration in a single PC. Preliminary testing produces unacceptably low frame rates (25Hz).

Google led me to the following site: https://www.derivative.ca/wiki088/index.php?title=Using_Multiple_Graphic_Cards which basically states that "all the work for all the processes get sent to the fastest GPU, and only the final images are sent across to the other GPUs to get displayed on-screen".

I cannot find any other information on the net to support this statement. Can anyone confirm that this statement is true?

Thanks in advance.
 

Shalaska

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Jun 17, 2015
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I have not tested it as I am at work right now, but one quick way to test it is to run a tool such as MSI afterburner and check the percent utilization and core speeds of your graphics cards. If all of the work is being sent to one card you should see one idling at near 0% while the other is at 100% and the same thing will be shown in the core speeds as one boosts and the other does not. That said I have no reason to believe that site to be incorrect and from the sounds of it you required the professional grade quadro cards not the consumer grade geforce cards.
 

CryoWolf

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Aug 20, 2014
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You're going to really have to Sli them in the same pc if they are both the same, you might as well since they are two 970's. When in Sli it splits the work across the two gpu's (ram will still be 3.5). You will see better performance including the sli bridge as long as the rest of the system supports it for simulation. From what I recall about nonsli was just having a quadro beside my main gpu for extra displays years ago. But for any task like simulation you should use the bridge. But this is for four screens. I would recommend radeons and use eyefinity.
 

Shalaska

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CryoWolf, the problem is that you cannot SLI them and have the screens on multiple cards so that will not work for their intended use case. With SLI all monitors must be attached to the same card, and since the 970 does not have the ability to connect 5 monitors SLI will not work in this case.
 

JustinSch

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Jun 19, 2015
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Hi. Thank you both for you responses. I have run several comparisons with various configurations and compared the numbers. This was using a test scene which has less detail then the final application. Also I only used 4 monitors (2 on each 970).

Single window, 7680x1080, Frame Rate=37Hz, GPU1 Core=1316Mhz, GPU1 usage=66%, GPU2 Core=873Mhz, GPU2 usage=10%
Two windows, 2x 3840x1080, Frame Rate=48Hz, GPU1 Core=1252Mhz, GPU1 usage=59%, GPU2 Core=1075Mhz, GPU2 usage=13%

For interest I also tried 2 windows but overlapped them on the monitors connected to a single card:
Frame Rate=71Hz, GPU1 Core=1239Mhz, GPU1 usage=71%, GPU2 Core=135Mhz, GPU2 usage=0%


Quadro Cards: These may have been a better option as the SLI Mosaic option may be what we want to achieve. Cost is however a consideration (as always).

SLI the 970s: leaves us with insufficient outputs.

AMD Eyefinity: Again cost is a factor. The W9100 would on paper do the trick but is prohibitively expensive. Would you be able to recommend a less expensive AMD card that will do the job? The W600 also has 6 outputs but only 2GB of GPU RAM.

Would you guys have any experience with display hubs such as the MST Hub (http://www.club-3d.com/index.php/products/reader.en/product/mst-hub-1-3.html) or Matrox TripleHead2Go (http://www.matrox.com/graphics/en/products/gxm/th2go/displayport/). I fear I may be asking too much of the GTX970 with this kind of setup.