Does running more monitors tax GPU performance?

Coldblackice

[H]ard|Gawd
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All else being equal, theoretically, if you're pushing a GPU to its processing limits in a game, would there likely be any tangible performance increase by turning off a second/third display (which is not being used in the game, just sitting at the desktop)?

Assume that the GPU is the limiting factor of the system.
 
Turning off the display? That won't do anything, you're GPU will still be processing the image, the monitor just won't show it.

I know you meant disable the display. If you disable the second display before gaming, so you'll only see a black screen on that monitor (even with it on) you will free up some video ram.

Will you free up GPU? Probably not much if any. Because when you game on a multi monitor setup but only use 1 monitor the other displays are just static images of your desktop, not much for the GPU to do.
 
If the GPU is not rendering any new information the GPU usage is more or less 0%

As for the frame buffer, assuming the display is 1080p that requires 8.3MB (per screen at 32bpp) which is 0.003% of your available frame buffer (assuming your frame buffer is 3GB).

Is 0.003% tangible? by definition, any figure above 0 is "tangible" so yes. It is also a tangible waste of time to bother disabling the screens.
 
One thing I found is that in crossfire if I don't disable my other monitors I run into micro stutter and choppiness.
 
Gaming while running a secondary display does not have nearly the performance hit it used to back in the early 2000s. FWIW I actually don't notice any performance difference whatsoever and I usually have widgets / temperature graphs, etc. on my portrait monitor while gaming.
 
The only way you are going to see any kind of performance hit is if you are running something on the 2nd screen that would tax the gpu. If im running 1080 video on my 2nd monitor while playing games, I take a very minor hit.
 
I'm not sure but one reason I got rid of my 7950 is it wouldn't run 2D/low power clocks with two monitors hooked up. It was always pushing midlevel 3D clocks (heat) and full RAM speed. Doesn't that indicate that the extra monitor is doing something, at least on the AMD hardware?
 
Does running anything on the second display require the game to run in windowed mode on the first one?
 
Gaming while running a secondary display does not have nearly the performance hit it used to back in the early 2000s. FWIW I actually don't notice any performance difference whatsoever and I usually have widgets / temperature graphs, etc. on my portrait monitor while gaming.

Yep, the main effect with dual monitors is the extent to which you enter full idle states. In other words, if you're doing trivial tasks such as VLC, browsing the net, etc - you will enter full idle clocks with Kepler and dual/triple monitor unless some program is triggering 3d clocks. Fermi was a nightmare in this respect (surround put you near 3d clocks all the time, even at the desktop), but Kepler fixed most of the dual/triple monitor power states so you will hit lowest idle clocks while using dual monitors or surround. You may need to use adaptive power management, but nonetheless.

As far as AMD hardware goes - With Tahiti and 7970s in CF (which I used), the lowest idle clocks and VRAM clocks are slightly higher (mid 500s? IIRC) while idling but I heard from a bud that this was fixed on the 290s. Also this was in 2012 (on Tahiti) so they may have adjusted the idle power states for dual screen/eyefinity, but this isn't related to OP's question per se.

Also to answer the question in the OP: Basically with any recent hardware, the answer is no. You won't gain performance by turning a display off. 2D windowed stuff is very, very undemanding on GPUs and basically requires near no attention, unless you're doing something like video encoding or anything along those lines. If you have a twitch or browser window open on a second screen, it will not affect performance, generally speaking.
 
It actually can affect performance indirectly via power throttling. I've noticed on my 7950 Boost that in addition to running at higher idle clocks (500/1400 instead of 300/150), I run into more situations where it reaches the (+20%) power limit and starts throttling the core clock, when it wouldn't with only one monitor.

I was playing the first level of the BF4 singleplayer campaign with two monitors connected to my 7950. I was getting a pretty steady 80ish FPS (Ultra but with MSAA off). Then, in a particularly action packed scene, my FPS tanked down to like 45 - I saw in the Afterburner graph that my core clock had dropped to 850 (instead of my 1100 MHz overclock) - meaning it had hit the power limit and throttled. Of course it doesn't always go down that low, but I noticed the core clock line was pretty wiggly up and down throughout the level.

Playing through the same scene with my second monitor hooked up to the onboard Intel HD 4600, and only my primary monitor connected to the 7950, the core clock line is an unwavering straight line at 1100 MHz, and the intensive part that caused problems before was nice and smooth.

Of course, it doesn't always happen, (it can vary a lot depending on the game and the scene whether it throttles), but I just noticed in general with two monitors hooked up, the core clock line wasn't as stable, and it affected my framerate. I'm sure whether this is an issue also varies depending on your video card too. But in any case, I just leave my second monitor hooked up to the integrated GPU and don't worry about it.
 
Never noticed a performance hit running dual monitors. Even if it were, I'd imagine it would be so minuscule for anyone to notice.
 
It depends. I know everyone else has stated that it doesn't effect it, but I've noticed a huge performance drop with my 2nd monitor enabled unless I disable Windows Aero. I prob get 20fps higher and less stutter in BF4 with Aero turned off.
 
I'm not sure but one reason I got rid of my 7950 is it wouldn't run 2D/low power clocks with two monitors hooked up. It was always pushing midlevel 3D clocks (heat) and full RAM speed. Doesn't that indicate that the extra monitor is doing something, at least on the AMD hardware?

Just wanted to say, I had this exact same issue when I was running 2x 4870x2 in quad crossfire. What I did to "fix" the issue was that I enabled my onboard Intel HD video and used that to run all of my secondary monitors instead. With my 2x 4870x2 powering only my main monitor, and my Intel HD Video powering my two secondary displays, idle clocks appeared to work normally.

This configuration should also alleviate any concerns about secondary displays hindering your GPU performance, as they wouldn't be handled by your main GPU anymore.
 
I run 2 monitors but my second monitor is the onboard intel gpu and always stays on
 
One thing I found is that in crossfire if I don't disable my other monitors I run into micro stutter and choppiness.

I had this and decreased c.f. usage if I used my receiver with my second monitor via hdmi for surround sound. Does using Intel igpu increase cup temps?
 
Just wanted to say, I had this exact same issue when I was running 2x 4870x2 in quad crossfire. What I did to "fix" the issue was that I enabled my onboard Intel HD video and used that to run all of my secondary monitors instead. With my 2x 4870x2 powering only my main monitor, and my Intel HD Video powering my two secondary displays, idle clocks appeared to work normally.

This configuration should also alleviate any concerns about secondary displays hindering your GPU performance, as they wouldn't be handled by your main GPU anymore.

I would have done that but I have a P67 mobo and K CPU. No onboard video allowed. Quirk of the times I guess.
 
I had this and decreased c.f. usage if I used my receiver with my second monitor via hdmi for surround sound. Does using Intel igpu increase cup temps?

It might increase it a few degrees, but likely nothing substantial. It doesn't stop me from hitting 5Ghz with my 2500k using a $20 air cooler.
 
One thing I found is that in crossfire if I don't disable my other monitors I run into micro stutter and choppiness.

check and see if windows aero is actually disabling it's self.. had this happen with my 8800GT's(yeah i know they're old as shit) multidisplay aero was using ~180mb of vram. disabling it dropped it down to 58mb. may or may not help but worth a shot if you are some how hitting your vram limit.
 
check and see if windows aero is actually disabling it's self.. had this happen with my 8800GT's(yeah i know they're old as shit) multidisplay aero was using ~180mb of vram. disabling it dropped it down to 58mb. may or may not help but worth a shot if you are some how hitting your vram limit.

Don't think it was a VRAM thing since I had 2GB and on one GPU it works fine, but thanks for the advice.

Multiple monitors and AMD have always gave me problems. See this thread I made for Bioshock infinite for example.

http://hardforum.com/showthread.php?t=1778681&highlight=

I had to disable my displays, log off, then log back in for the game to be smooth.
 
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