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Higher CPU usage with new GPU?

Last response: in Graphics & Displays
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December 2, 2012 1:02:42 PM

Hello,

I recently upgraded to a GTX 670 (from a 470) and it seems that the cpu (i5 2500k unclocked) usage is a little higher when I'm watching HD videos than it used to be. This only applies when I'm watching videos (specifically HD videos) and not when I'm playing games, like skyrim for example.

It's typically around 10-15% when I'm watching a 1080p video in VLC, I don't think it used to be that high. Any ideas what could be causing this??

Btw, after I enabled GPU acceleration in VLC, cpu usage is down to ~2% which is great, but I'm still wondering why it's so high without it?

More about : higher cpu usage gpu

December 2, 2012 1:04:56 PM

The CPU 'feeds' the GPU, and the faster the GPU goes through stuff, and the more it processes the more it needs to be fed.
December 2, 2012 1:13:29 PM

scannall said:
The CPU 'feeds' the GPU, and the faster the GPU goes through stuff, and the more it processes the more it needs to be fed.


Thanks for your answer! I can understand how this would be if I was playing a game, with higher details settings and higher fps rate etc, but what is the difference between watching a HD video with the two different graphic cards? What kind of extra information does the new graphics card process that the old one didn't?
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December 2, 2012 1:23:34 PM

ArtfulBotcher said:
Thanks for your answer! I can understand how this would be if I was playing a game, with higher details settings and higher fps rate etc, but what is the difference between watching a HD video with the two different graphic cards? What kind of extra information does the new graphics card process that the old one didn't?


Your graphics card doesn't have anything to do with it. You had software rendering enabled when you saw the higher load. Basically all of the rendering was being done on the CPU. Depending on the driver this can go up or down when you switch graphics cards. Once you enabled GPU acceleration the rendering shifted to the graphics card, hence your load dropped to 2% (which is normal for an idling CPU).
December 2, 2012 1:41:10 PM

ddpruitt said:
Your graphics card doesn't have anything to do with it. You had software rendering enabled when you saw the higher load. Basically all of the rendering was being done on the CPU. Depending on the driver this can go up or down when you switch graphics cards. Once you enabled GPU acceleration the rendering shifted to the graphics card, hence your load dropped to 2% (which is normal for an idling CPU).


Ok, so if I got this right, it depends on the drivers for the graphics card? Isn't ~15% a little high for watching a video, or is this 'normal'. I read somewhere that modern CPU's generally stay below 10% when watching HD videos.
December 2, 2012 2:35:07 PM

ArtfulBotcher said:
Ok, so if I got this right, it depends on the drivers for the graphics card? Isn't ~15% a little high for watching a video, or is this 'normal'. I read somewhere that modern CPU's generally stay below 10% when watching HD videos.

Well I have an i5 2500k with a 7850 and while watching a 720P movie my usage is only 5%
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December 2, 2012 3:42:52 PM

ArtfulBotcher said:
Ok, so if I got this right, it depends on the drivers for the graphics card? Isn't ~15% a little high for watching a video, or is this 'normal'. I read somewhere that modern CPU's generally stay below 10% when watching HD videos.


I think you misunderstood me. The 15% doesn't count because your CPU's doing the work. What you should look at is the 2% number because that's your graphics card doing the work. Just remember to leave hardware acceleration/rendering enable for whatever your using (most should have by default, VLC tends to be the exception).

The reason it looked so high is because VLC wasn't using any of the features built into hardware to render the video. It's only using the basic operations available, this makes it less efficient and uses more resources. This main reason for the big push to incorporate more video decoding resources into the hardware.
December 2, 2012 4:07:29 PM

ddpruitt said:
I think you misunderstood me. The 15% doesn't count because your CPU's doing the work. What you should look at is the 2% number because that's your graphics card doing the work. Just remember to leave hardware acceleration/rendering enable for whatever your using (most should have by default, VLC tends to be the exception).

The reason it looked so high is because VLC wasn't using any of the features built into hardware to render the video. It's only using the basic operations available, this makes it less efficient and uses more resources. This main reason for the big push to incorporate more video decoding resources into the hardware.


Ok, I think I'm with you there, but I never used to have hardware acceleration on before, or at least I don't think so. As far as I know it's not on by default in VLC (it's marked 'experimental') and I've never messed around with any of the options. So what I'm wondering is why the CPU is doing more work now than before, if hw acc was off in both cases?
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December 2, 2012 5:33:37 PM

ArtfulBotcher said:
Ok, I think I'm with you there, but I never used to have hardware acceleration on before, or at least I don't think so. As far as I know it's not on by default in VLC (it's marked 'experimental') and I've never messed around with any of the options. So what I'm wondering is why the CPU is doing more work now than before, if hw acc was off in both cases?


Seems like you've got it for the most part. The reason for the difference could be a number of things. Because the videos have to go through the graphics driver regardless of the rendering method (to display something) my guess is by changing the video card there was a change in the driver (however minor) that caused the difference. One of the issues that I have with VLC is they tend to mark stuff as experimental when it's been around and stable for a long time, while brand new stuff (say Blu-Ray support) is buggy at best and is marked as stable.
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