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144HZ - very high power consumption

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144HZ - very high power consumption

Postby crun » 09 Apr 2014, 11:05

I noticed that since I've upgraded my monitor to 144HZ, my power consumption in idle jumped to 120-130W in idle from 70-75W.
When I decrease my refresh rate to 120HZ in screen resolution settings, it goes back to around 70W.

I see that GPU does not clock down @ 144HZ settings. It does at 120 and 121HZ though...

Is there any fix for this? I would like to use my 144HZ fully, because I don't really enjoy strobe (=120HZ)
One I found is to set 121HZ in Windows and force in NVIDIA Control Panel 3D global settings preferred refresh rate to highest available. But then only fullscreen games would run 144HZ, correct?

I am using NVIDIA GPU (780 with custom bios, but it doesn't really matter I guess). I am running two screens (both 1080p, second monitor is 60hz) and W8.
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Re: 144HZ - very high power consumption

Postby RealNC » 09 Apr 2014, 11:28

It's by design and it was NVidia's decision. I doubt that they will change it. It seems that 144Hz is too fast to hide the flicker caused by power state changes, and NVidia went with disabling power savings completely when in 144Hz.

As far as I understood the problem, this is why they did that:

Normally, when the power state of the GPU changes, there's a small time interval that's needed in order for that change to complete. During that time, the GPU can't send correct frames to the monitor. With lower refresh rates, this doesn't show up since the state change takes less time then the monitor needs to begin scanning out a new frame. In 144Hz, the monitor needs less time to start the next frame and the GPU doesn't have enough time anymore. The result would be a visible screen flicker of maybe one frame. That means the screen would flicker whenever you do something that would raise the current power state of the GPU (like scrolling in a web page, for example.)

I'd recommend 120Hz on the desktop. Use 144Hz only for games.
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Re: 144HZ - very high power consumption

Postby Chief Blur Buster » 09 Apr 2014, 11:38

crun wrote:Is there any fix for this?

You could use a third party resolution switching utility to allow switching between 120Hz and 144Hz via an easy system tray click.

RealNC wrote:It seems that 144Hz is too fast to hide the flicker caused by power state changes, and NVidia went with disabling power savings completely when in 144Hz.

RealNC, do you know where the original post/source was, that explained the 144Hz power mode switches? There is no flicker involved from what I know (except in laptops). The GPU dotclock is constant and the output of the frame is accurate to microseconds, regardless of CPU load, so there would be no flicker involved. However, there could be other reasons, and I am curious.

(you see these numbers in Custom Resolution Utilities)
Dotclock = number of pixels per second. They never delay by a single pixel, regardless of CPU load
Horizontal scan rate = number of rows of pixels per second
Vertical scan rate = number of refresh cycles per second

The dotclock remains an immovably exact value, so at a 150MHz dotclock, the beginning of a refresh cycle is exact to 1/150,000,000th of a second, regardless of whether CPU/GPU load is 0% or 100%. So I'm wondering if there's some misinformation somewhere else on the Net, or if NVIDIA described it in a way that was confusing. Or that flicker was caused by a GPU behavior defect, or power regulation issues (e.g. sudden change in power requirements within the graphics boards that was amplified at 144Hz) that caused flickering, etc. So you could be right in that first part of how you described things, e.g. needing to fit a power state change in the blanking interval -- and 144Hz does have a much smaller blanking interval.

I'm pretty curious, so I've fired a question to NVIDIA.
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Re: 144HZ - very high power consumption

Postby RealNC » 09 Apr 2014, 11:38

There doesn't seem to be official word on this from NVidia. Doing a search for "nvidia 144hz gpu clock" or similar will turn up posts/articles on people speculating.

If you have connections, you might want to ask them :) 144Hz is a pretty important thing for the users of Blur Busters.

It does make sense to me, however. I remember early (open source) drivers of my old Radeon card having flicker when changing power states. A patch was submitted at some point that fixed it by timing the power state change in such a way that the monitor won't notice. I assume that 144Hz is so fast that timing this correctly might be very difficult.
Last edited by RealNC on 09 Apr 2014, 11:52, edited 6 times in total.
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Re: 144HZ - very high power consumption

Postby crun » 09 Apr 2014, 11:39

Is there any simple, light weight program with which I could switch between 120HZ/144HZ via global keybind?

Oh, and:
(...)set 121HZ in Windows and force in NVIDIA Control Panel 3D global settings preferred refresh rate to highest available. But then only fullscreen games would run 144HZ, correct?
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Re: 144HZ - very high power consumption

Postby Chief Blur Buster » 09 Apr 2014, 11:43

crun wrote:Is there any simple, light weight program with which I could switch between 120HZ/144HZ via global keybind?

PowerStrip has long been used for this. MultiRes is a utility that can do it easily via mouse. Both are available at www.entechtaiwan.com ... However, these tools are gradually getting dated, and we need modernized versions of similar tools.
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Re: 144HZ - very high power consumption

Postby Chief Blur Buster » 09 Apr 2014, 11:45

RealNC wrote:There doesn't seem to be official word on this from NVidia. Doing a search for "nvidia 144hz gpu clock" or similar will turn up posts/articles on people speculating.

I did some more reading, and it does indeed seem to suggest that power state changes disrupt the graphics output. Could be momentary loss of dotclock for a brief moment (and not enough time in the blanking interval to hide the disruption). There are many reasons why changing power states could possibly disrupt the GPU output.
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Re: 144HZ - very high power consumption

Postby RealNC » 09 Apr 2014, 11:51

Chief Blur Buster wrote:I did some more reading, and it does indeed seem to suggest that power state changes disrupt the graphics output. Could be momentary loss of dotclock for a brief moment (and not enough time in the blanking interval to hide the disruption). There are many reasons why changing power states could possibly disrupt the GPU output.

Found this from the Radeon driver (http://xorg.freedesktop.org/wiki/RadeonFeature):

The "dynpm" method dynamically changes the clocks based on the number of pending fences, so performance is ramped up when running GPU intensive apps, and ramped down when the GPU is idle. The reclocking is attemped during vertical blanking periods, but due to the timing of the reclocking functions, doesn't not always complete in the blanking period, which can lead to flicker in the display. Due to this, dynpm only works when a single head is active.
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Re: 144HZ - very high power consumption

Postby ManuelG_NVIDIA » 09 Apr 2014, 12:44

This is by design when running dual monitors and one of the monitor is running at 144Hz. This change was made a few driver versions ago to prevent a display glitch when driving at such high frequencies with dual monitors. As you stated, it only affects the graphics card if running in dual monitors where one of the monitors is running at 144hz
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Re: 144HZ - very high power consumption

Postby Chief Blur Buster » 09 Apr 2014, 12:56

Thanks, Manuel, for your quick response!

In all cases, even at 144Hz, the power still throttles back when the display goes into standby, as I understand it. So the high idle power consumption won't continue to occur if you've left the computer on, and gone to bed for the night.
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