Multiple displays with single GPU

[zCypher]

Hey y'all,

I finally bought a TV, and after hooking it up to my PC, I realize that unless I'm doing something wrong, I've encountered some kind of limitation.

I'm using a 7970 which has two DVI ports and an HDMI port. Up till now, I've been using a Dell U2713HM @ its native 2560x1440, and an older Samsung at its native 2048x1152. No issues with that in terms of using these two screens together.

When I hooked up the TV, I noticed two things. It would not allow me to extend my desktop across all three screens in the same manner that I had been doing with two screens. I had to choose to have one of them mirroring/displaying identical content to the other, effectively not giving me three screens of space, or use only two.

The other thing is that with all 3 connected, it limits me to 1080p on my two monitors! Even after unplugging the TV, it took quite a bit of fiddling to get my Dell back to its proper resolution.

So I'm not too sure if this is just by design with this GPU, or what. Has anyone else trying to use 3 displays on one GPU encountered similar results?

The TV otherwise seems to work fine, but I'm a little put off that I can't simply use all three displays in a triple screen setup all at their full native resolutions. Any tips or suggestions (other than buying a second GPU) would be welcome!

 

[rc3ilynt]

Have you tried to play with eyefinity/multidisplay profiles in catalyst?

 

[lupi]

to use 3 outputs on that card, believe at least one must be via displayport.

 

[KingFatty]

Yes, you need to have at least one display using the displayport output of the card, which means you'll need a displayport cable or a $25 active displayport adapter if none of your displays support displayport. Does your 2560x1440 display have a displayport input you can use, or is it DVI only?

I did triple output from a 7950 card, and found the best results when I put the 2560x1440 display on the displayport.

 

[zCypher]

Thanks for the feedback. I think my U2713HM has displayport, so I could try that, just need to find myself a cable to test with. So if I have 1 on displayport, 1 on DVI and 1 on HDMI, there is yet hope to get this all playing nice?

A not quite related question: anyone notice that video playback over HDMI turns the screen completely black during a scene that is all dark? I play the same scene on my computer monitor, and it doesn't do that. That part of the scene definitely looks 'all black', but when played on the TV through HDMI, it looks like as soon as that scene arrives and it's all black, it's almost as if the signal is cut completely and the screen is even blacker, almost like it flickers darker for a sec. If there is any other content on the screen at the time of that scene, it doesn't do it (for example, if i'm moving the mouse around).

Can't find any settings in the AMD drivers that would impact this. I might just be nitpicking, but maybe someone knows about this.

edit: tested two different HDMI cables and different HDMI ports on the TV. same effect in each case. hmm

 

[zCypher]

So looks like the GPU is "mini display port" and the monitor is "display port". I see there are "mini display port to display port" cables, hopefully this should do the trick.

 

[lupi]

What type f TV is it? If it is a monitor/TV, then some have known issues when connected to a pc via hdmi.

 

[zCypher]

I think I've figured out what's happening. It isn't related to HDMI after all. I tested both my HDMI cables on my Dell monitor and it doesn't happen. I looked this up and it seems that most likely culprit is the "dimming" feature. There are a bunch of long threads on similar issues that I found, and certain TV sets are able to disable the feature outright, others don't let you disable it, but it gets disabled during certain configurations/modes.

In my case I don't have any option to disable dimming anywhere, and PC, cinema or game mode don't change anything for that. The one thing I found after running through all the settings and trying all the steps others have tried, is that setting blacks to high actually makes this feature stop completely, for some reason.

That's really quite annoying as it looks substantially better with blacks on low, otherwise.

yargh. there aren't really any better deals around, so even if i do find a set i like more, i will lose money returning and upgrading. i guess i will throw this on the wall and try it proper before making up my mind. i can't be the only one put off by such a 'feature' though..