Michael 2006-05-09 10:06
Hi! I have a system with two ATI Radeon video cards (one PCI express, one PCI). Both are dualhead.
I'm trying to develop an app for 3 monitors (2 on the pci express card, one on the PCI card). Using OpenGL, I've encountered very low frame rates if I just open a full screen window on each monitor. I suspect it's falling back to software rendering or something.
Could anybody point me at documentation or (even better) example code that uses multiple monitors via multiple video cards? I'd really appreciate it!
Thanks so much!
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Lennart 2006-05-09 22:17
Hi
I only have success using multiple Nvidia cards for hardware accelerated OpenGL accross screens.
I've successfully used 3 PCIe 16x Nvidia 7600 cards with a total of 6 screens.
You do not need to adjust your application in order to do this.
Just make sure the advanced settings in the driver is set to multi screen acceleration.
Lennart
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Michael 2006-05-12 11:03
Well I'm using ATI cards. I've looked all over the settings and everything regarding accelleration seems to be enabled.
But as I add the third monitor (via the second card), the framerate drops a ton (from ~100 to ~17)
Any other ideas? I'd really appreciate any help!
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ECarlson 2006-05-12 11:53
It is a possibility that only NVidia currently supports OpenGL hardware acceleration across multiple outputs on multiple cards, so there is a chance that you'll have to replace those ATI cards with NVidia cards to do what you want to do.
If you find out that it can be done with ATI cards, please post how it's done. Also, if you end up getting NVidia cards, and that works, please let us know.
- Eric, www.InvisibleRobot.com
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yair 2006-05-14 07:12
i have tried and fialed getting 3 opengl secreens with ati cards or witha cobination of both.
2 nvidia cards (i used a noname geforce 5200fx) gave me this with on boot,!
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Michael 2006-05-25 05:42
I bought a dualhead PCI16 nvidia card (GeForce 6200) and a singlehead PCI card (GeForce 5200).
I can get two monitors working by using the Horizontal Span mode on the dualhead card, but I can't get anything on the third monitor (via the second card).
It seems that any time I create a window that's not on the monitor that's set as primary (in Display Settings), OpenGL does not render anything. I just get a blank window. And since you can only have one primary monitor, this is a major problem for me.
I've checked in the nvidia settings, and multi-display accelleration is enabled on both cards...
Any ideas?
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ECarlson 2006-05-25 10:50
Have you tried any other OpenGL apps? Maybe it only works with certain or newer cards. Maybe Lennart has some more ideas.
- Eric, www.InvisibleRobot.com
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Michael 2006-05-31 02:59
I just wrote my own OpenGL app that opens two windows and displays a rotating cube in each.
If I have one window open on the primary screen (which actually spans 2 monitors via horizontal span) and one open on the secondary screen (driven by the 2nd card), only the first one renders. If I drag the second one onto the first screen, then they both render...
Whatever I do, I can't get both cards to render something at the same time.
Any ideas? Or anybody know of a good application I could use for testing? Maybe I'm doing something wrong...
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ECarlson 2006-06-01 01:22
Try switching the first card out of span mode.
- Eric, www.InvisibleRobot.com
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anon 2006-06-02 02:16
I am unaware if this is still the case, but it used to be an artificial driver limitation, so... you "may" be successfull with a hacked firegl driver.
I have had to deal with this problem before, but don't know the current situation.
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anon 2006-06-02 02:16
"Try switching the first card out of span mode."
That kindof defeats his project doesn't it?
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Ralph Seguin 2006-06-02 13:57
For what it is worth, I encountered a similar problem yesterday on a PowerMac G5.
Config: PowerMac G5, 8GB RAM, 250GB disk, NVidia QuadroFX 4500 PCIe (512M) + NVidia 6600 PCIe (256M), OS 10.4.4, qty=4 screens, configured as a single large screen, tiled 2x2.
Problem: We were driving 4 displays simultaneously @ 1920 x 1080 @ 60 Hz.
I could play a quicktime movie or run an OpenGL program in one of the displays at full speed, but as soon as I moved or grew the window such that it spanned more than one display, the frame rate dropped from 60Hz to about .2Hz or so. A pretty noticeable drop!
It is clearly NOT a bandwidth or bus contention issue (in my mind at least), since I was able to run 4 Quicktime movies or OpenGL simulations fullscreen in each of the 4 displays without any slowdown in any of them. As soon as the window spanned more than one display, everything went to crap.
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ECarlson 2006-06-02 16:14
Anon: No, I don't think that defeats his project, but I could be wrong. He said he wants full speed OpenGL on all 3 monitors. If that works when he turns off span mode, how does that defeat his project?
- Eric, www.InvisibleRobot.com
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Michael 2006-06-09 01:48
I can turn off Span mode (and use "Dual View" instead) and still get it to display on two monitors, but I still get nothing on the 3rd. The window opens and nothing renders. :-(
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ECarlson 2006-06-09 15:03
Does the same happen when you use other OpenGL apps on the 3rd screen? (I asked this question before, but I didn't notice an answer.)
- Eric, www.InvisibleRobot.com
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Thomas 2006-06-13 01:35
On my system (2x 7800GTX, no spanning) it works OK. A 2048x1536 (desktop size) movie rendered via OpenGL runs at least with 25fps, and my small OpenGL application runs with 60fps (about 100,000 vertices and some small textures).
But when I turn on display spanning, one spanned display is blank.
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Allan 2006-07-08 02:50
I have (2) nvidia 7600GT PCI-E with dualhead each, I can only get (2) to work on horizontal span mode (the 2 that are hooked to the same card) and the 3rd monitor working as indpendent stand alone.
Is it even possible to have horizontal span on all 3 monitors? or do I need a single card with 3 heads?!
please help
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