Question about using 3 monitors and 3 GPUs

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mataniko

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Aug 8, 2008
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Hi,
I am unsure about how such a setup works:
I have 3 monitors, a 26" LCD, a 42" HDTV both connected on a GTX 280 and a 8400GS connected to a 15" side monitor.
Besides applications that let you choose which video card to use, is there any way to determine which video card is the one being used? if something is dragged to the side monitor, will that GPU kick in for that application?

Basically my question is: Is it possible to render something using the GTX while outputting to a monitor not directly connected to it?

Thanks
 
To see specifically which one is which you can go into the Displays control panel and it will say "Monitor X" on "Video Card X" ie. 1. 26" LCD on GTX 280 and "2. HDTV on GTX 280"
 
so if i have a window open between two screens who it's being rendered by two cards?
 
mataniko said:
Basically my question is: Is it possible to render something using the GTX while outputting to a monitor not directly connected to it?
Click to expand...

To the best of my knowledge, there's no way for that to happen.
 
mataniko said:
so if i have a window open between two screens who it's being rendered by two cards?
Click to expand...

not to be a dick, but you're basically going all hysteria whine and cry over nothing, and making this far more complex than it needs to be, unless you really have a need (read this: NEED) to span a 3D application across multiple displays, what you're asking about doesn't matter, abstraction exists for a reason

also, in a generaly 2D desktop environment, nothing is being "rendered" in the sense you're referring to, it isn't that big of a deal, so on and so forth


Oldie said:
To the best of my knowledge, there's no way for that to happen.
Click to expand...

unless you have some very expensive and proprietary stuff (we're talking five figures), but it usually is not realtime (unless you want to spend more)
 
I have 3 monitors, a 26" LCD, a 42" HDTV both connected on a GTX 280 and a 8400GS connected to a 15" side monitor.
Click to expand...

So far so good...

Besides applications that let you choose which video card to use, is there any way to determine which video card is the one being used? if something is dragged to the side monitor, will that GPU kick in for that application?
Click to expand...

Use device manager or nvidia control panel to see what cards are running which displays. But you've already told us. The GTX 280 is running the 26 and 42. The 8400GS is running the 15.

Basically my question is: Is it possible to render something using the GTX while outputting to a monitor not directly connected to it?
Click to expand...

No the card must be physically connected in order to render to a monitor.

I think what you might be confused about is desktop spanning. In this case, your GTX 280 can span two displays, the 26 and 42 into one. So you can drag a window from the 42 and 26 and vice versa. When you see a window that is 'in between' the two displays, the GTX 280 is rendering to BOTH displays at once, BUT the individual input lags of the monitors become involved so the window may not be rendered equally fast on both monitors.

However in the above case you cannot drag a window from the 26 or 42 to the 15. Why? Because the GTX 280 is rendering to the big monitors and the 8400GS is rendering to the 15, and the GTX 280 is NOT linked to the 8400 GS in any physical way (ie by a bridge.) And if you want to ask if you can link a GTX 280 to a 8400 GS, the answer is NO. In SLI the video cards must match.
 
vjcsmoke said:
However in the above case you cannot drag a window from the 26 or 42 to the 15. Why? Because the GTX 280 is rendering to the big monitors and the 8400GS is rendering to the 15, and the GTX 280 is NOT linked to the 8400 GS in any physical way (ie by a bridge.) And if you want to ask if you can link a GTX 280 to a 8400 GS, the answer is NO. In SLI the video cards must match.
Click to expand...

Actually here's where you're incorrect. I'm currently running 3 monitors on a 4850/2600 combo. Two on the 4850 and one on the 2600. I can span a video across all 3 or even watch the video uninterrupted while dragging it from a 4850 connected display to a 2600 connected display (provided it's not 1080p or something the 2600 can't handle).

I'm kind of curious to see what happens with a windowed game, but I get the feeling it won't be able to run on the 2600 screen.
 
Oldie said:
Actually here's where you're incorrect. I'm currently running 3 monitors on a 4850/2600 combo. Two on the 4850 and one on the 2600. I can span a video across all 3 or even watch the video uninterrupted while dragging it from a 4850 connected display to a 2600 connected display (provided it's not 1080p or something the 2600 can't handle).

I'm kind of curious to see what happens with a windowed game, but I get the feeling it won't be able to run on the 2600 screen.
Click to expand...

this.

SoftTH claims that with its newer editions it can actually handle triple head on a setup like yours, although I don't know how well this works (or how well SoftTH works in general, their documentation is somewhat vague, and all of their "explanations of the process" look entirely copied from the original Matrox presentations on Parhelia and GXM)

with a professional grade solution (meaning QuadroFX, FireGL, REALiZM, or something...larger), you can drag/render across multiple displays (and in many cases, across multiple machines connected to multiple displays), although this is done in OpenGL with quite a bit of extra software, and ideally you've got a house clock fed into all of the cards so everything is timed right

basically, the hardware can physically do it, and to a degree software can do it, but not all software will play nicely in this manner, if you do decide to try SoftTH out (or some similar implementation), I'd love to hear about it, mostly because I've yet to actually read any credible/3rd party review/discussion of SoftTH beyond their website (and I lack the extra monitors (or desk space, or time) to screw with it myself)
 
ive run a windowed game across 3 screens with two separate cards, supcom to be exact. Hardware is in my sig.

edit: oh and WoW too.
 
mataniko said:
...

Basically my question is: Is it possible to render something using the GTX while outputting to a monitor not directly connected to it?

Thanks
Click to expand...

Yes. SoftTH does tha, and it is freet. So it will use let's say your GTX to render an image for all 3 displays, then it cuts up the rendered image into the 3 lcd sizes, then send the image through the pcie bus to the secondary card to display the side images on them.

Here is the image of this process.

The questions now is, "Why do you care?"

diagram.png
 
Guys thanks for the input, here are my findings:
The primary monitor as set by windows will be the one used to render any 3D applications you open, this window can be moved all around the 3 screen desktop, without changing GPUs. (Unless the applications allows you to choose which video card to use (Fallout 3 for example).

Spanning of video playback/3d apps across the desktops is done by the system and not the GPU.

To simplify my question:
If I run something that requires the GPU on a monitor connected to a secondary video card, would it be run by my main video card if the application does not allow you to pick the video card? The answer is "yes" if your primary monitor is connected to the primary video card.

Thanks
 
Last edited:
that image, tmk, is stolen from Matrox (one of my issues with SoftTH)


also, supcomm is one of a few games with excellent multimonitor support (count Empire Earth, Total Annihlation, and Bioshock in that as well)
 
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