Performance impact from duplicating display

[dancingcrab]

Hello all,

I've recently upgraded my GPU from a Radeon 4870 1GB to a GTX 560 Ti 448 (the MSI Twin Frozr III OC edition). It's pretty neat.

I have a new 1080p LCD display. The PC is also connected to a 40" 1080p television. I want to be able to switch between either display, but Nvidia's control panel isn't as useful as AMD's (which let me do this via hotkeys), so instead I set it to duplicate the display. I then played Skyrim for three hours, no problems, and went to bed. Thus I know Skyrim, at least, works fine.

However, when using a single display, my idle GPU temps are around 34-37C. I noticed this morning that the idle temps, with duplicate display active, was 46-47C! Set it back to single display, and temps dropped accordingly.

Now I don't have the opportunity to test anything right now, but I was hoping someone here could explain whether or not duplicating displays generally causes a performance hit? Seems strange to me, as surely the GPU doesn't have to render the image twice?

Thanks in advance for any information!

 

[Magic Carpet]

Makes GPUs drop 2D clocks basically. There is a work-around > NVIDIA Inspector.

 

[dancingcrab]

Makes GPUs drop 2D clocks basically. There is a work-around > NVIDIA Inspector.

Hi - thanks for the fast reply!

So are you saying that, with the regular software, when duplicating displays, the card operates at regular 3D clocks instead of lower 2D clocks? Thus, 3D performance is not affected when using duplicate monitors?

Will check out NVIDIA Inspector.

Thanks again!

 

[Magic Carpet]

Hi - thanks for the fast reply!

So are you saying that, with the regular software, when duplicating displays, the card operates at regular 3D clocks instead of lower 2D clocks? Thus, 3D performance is not affected when using duplicate monitors?

Will check out NVIDIA Inspector.

Thanks again!

Exactly, that's why your card runs so hot. The reason may not be related to performance though:

Since NVIDIA GDDR5 graphics card is used as a video store, there is a limitation on the power management features. If more than a single display with different resolutions / timings are connected to the graphics card, the drivers that automatically prevents downshift in energy-saving "Performance States (P-States).

The reason is, according to NVIDIA in a hardware limitation in the use of GDDR5 memory, which can cause change of P-states to flicker. This issue is therefore not limited to NVIDIA graphics cards.

Unfortunately, nVIDIA doesn't give you a chance to "enjoy" flickering (which I haven't noticed personally on my dual-monitor setup)... Fortunately, there is Inspector

 

[96Firebird]

Hotkey in Windows 7: Win + P

You can set it to duplicate when you want to do that, or you can extend, or enable only one of the displays. Pretty useful hotkey, I use it all the time when I want to watch movies on my TV. :thumbsup:

 

[dancingcrab]

Exactly, that's why your card runs so hot. The reason may not be related to performance though:

Unfortunately, nVIDIA doesn't give you a chance to "enjoy" flickering (which I haven't noticed personally on my dual-monitor setup)... Fortunately, there is Inspector

Inspector has cured all! No flickering here. Although I installed the Inspector and quickly ran the Section 8: Prejudice benchmark and it ran at 6-8fps... which was obviously concerning. I then realised I could activate the P0 state depending on the GPU load. Set it at 50%, seems to work great.

Hotkey in Windows 7: Win + P
You can set it to duplicate when you want to do that, or you can extend, or enable only one of the displays. Pretty useful hotkey, I use it all the time when I want to watch movies on my TV.

Awesome, thanks!

 

[Magic Carpet]

I am glad, you got it resolved. Now, you're ready for the new year

Get this to monitor your temps/voltage. And also check my other thread

 

[dancingcrab]

I am glad, you got it resolved. Now, you're ready for the new year

Get this to monitor your temps/voltage. And also check my other thread

This is gonna sound really n00b... but can undervolting damage a GPU? I'm currently running my card overclocked, so probably couldn't get away with it anyway, but I still interested.

For the curious:
Core at 850MHz, up from 750MHz (factory OC, up from 732MHz stock)
Shaders at 1700MHz, up from 1500MHz (factory OC, up from 1464MHz)
Memory at 4200MHz effective, up from 3900MHz (factory OC, up from 3800MHz)

All at stock voltage.

 

[Magic Carpet]

This is gonna sound really n00b... but can undervolting damage a GPU?

Short answer, no.

I'm currently running my card overclocked, so probably couldn't get away with it anyway, but I still interested.

For the curious:
Core at 850MHz, up from 750MHz (factory OC, up from 732MHz stock)
Shaders at 1700MHz, up from 1500MHz (factory OC, up from 1464MHz)
Memory at 4200MHz effective, up from 3900MHz (factory OC, up from 3800MHz)

All at stock voltage.

When you are overclocking, there isn't much left to undervolt. However, you could probably undervolt just your 2D clocks. There are 3 performance states available for your card which you could alter. However, most benefits come when it's "busy". I estimate, you could drop around 4W-8W off your Idle power consumption by doing so. This is not hell a lot, and if you're after saving watts in desktop mode, it's better to choose another design. Laptop for example. But I think it's going to change with next gen-hardware.

The reason I undervolted in the first place.. was the acoustics factor. It is very nice to have a dead-silent card under any load with only a $5 fan investment. Power savings are just a bonus.