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HD Radeon 6970 w/ 40" 1080p LED not running at 120hz

Last response: in Graphics & Displays
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May 3, 2012 11:17:27 PM

Hello!

I'm running an HD Radeon 6970 2GB GPU and I recently purchased Westinghouse 40" 1080p LEDTV w/ 120hz refresh rate to use as a monitor. Along with the television, I purchased a new HDMI cable that states it is full 1080p and runs at 120hz (I'm not a graphics guru but I wasn't aware there was an option for HDMI cables in this regard).

My issue is that Catalyst Control Center is showing that the maximum reported refresh rate is 75hz. I'm running at 1920x1080 resolution and, at this resolution which I thought was 1080p (thus the 1080 pixels of vertical resolution), the "crispness" of the picture is not much to be desired. The best way I can describe the picture is that it looks a bit blurry or out of focus when you look closely (i.e. things look almost "doubled up" if you look closely). Secondly, and I attribute this to the lack of refresh rate on such a big screen, I can notice a very subtle "lag" when I move the mouse around the screen. I'm thinking that this is because a screen of this size needs to be running at 120hz but obviously I can't be sure.

I'm going to pursue this on my own as well in the meantime but I wanted to put this out there to pull from the expertise of this community if anybody has a moment.

Thanks so much!

EDIT: As an update, I removed the HDMI cable and used standard VGA instead (although the card itself doesn't have a standard VGA port so I'm running that end of the VGA through a DVI (I believe) adapter. Now the "blurriness" and poor picture portion of it is resolved. The picture seems crisp now. I am, however, still battling the refresh rate. I'm going to throw a guess out there and say that I need to not use an HDMI or VGA but rather need to use the DisplayPort port instead. Any ideas?
May 4, 2012 12:08:41 AM

In the past HDMI has not been able to run 120hz at 1080p. If the option is available, it's only very recently. Even if you bought a cable saying it supports 1080p at 120hz, that does not mean that the TV can support that resolution and refresh rate.
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May 4, 2012 4:09:49 AM

bystander said:
In the past HDMI has not been able to run 120hz at 1080p. If the option is available, it's only very recently. Even if you bought a cable saying it supports 1080p at 120hz, that does not mean that the TV can support that resolution and refresh rate.

Thanks for the response, Bystander.

The TV is 1080p and 120hz refresh rate so your first point is probably the issue in that it has to do with the cable. I couldn't find anything about refresh rates based on resolution for my particular card but I'm willing to be that I need to use DisplayPort to output from my 6970 at 120.
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May 4, 2012 4:14:22 AM

HDTVs don't typically do true 120 Hz. That is, they don't accept a 120Hz input even if you give it to them - they just take a 60 Hz input and interpolate it up to 120Hz.

If you want to do true 120 Hz gaming, I'm pretty sure you need a 120 Hz monitor. Sorry :( 

cf., http://www.overclock.net/t/662628/60hz-vs-120hz-explain...

I could always be wrong, because I am not up to speed on the latest HDTV tech, but as far as I am currently aware, TVs cannot do true 120 Hz that a PC gamer would want.
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May 4, 2012 4:39:18 AM

BigMack70 said:
HDTVs don't typically do true 120 Hz. That is, they don't accept a 120Hz input even if you give it to them - they just take a 60 Hz input and interpolate it up to 120Hz.

If you want to do true 120 Hz gaming, I'm pretty sure you need a 120 Hz monitor. Sorry :( 

cf., http://www.overclock.net/t/662628/60hz-vs-120hz-explain...

I could always be wrong, because I am not up to speed on the latest HDTV tech, but as far as I am currently aware, TVs cannot do true 120 Hz that a PC gamer would want.


They still can't do 120Hz, their inputs are limited to 60Hz. Additionally, a lot of 120Hz monitors will likewise cap their HDMI (and only their HDMI inputs to my knowledge) at 60Hz.
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May 4, 2012 4:44:03 AM

I don't think he meant monitors using HDMI. Just 120hz monitors in general, which all use DL-DVI or DP as far as I'm aware.
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May 4, 2012 4:53:49 AM

JoshDBoyle said:

EDIT: As an update, I removed the HDMI cable and used standard VGA instead (although the card itself doesn't have a standard VGA port so I'm running that end of the VGA through a DVI (I believe) adapter. Now the "blurriness" and poor picture portion of it is resolved. The picture seems crisp now. I am, however, still battling the refresh rate. I'm going to throw a guess out there and say that I need to not use an HDMI or VGA but rather need to use the DisplayPort port instead. Any ideas?


Does the TV have a DisplayPort input? If so, that would be the best input available, which has a chance to work at 120hz, if the TV actually supports true 120hz (not likely).

Also, about that HDMI. Did it say it supports up to 120hz and also supports up to 1080p? HDMI can receive 120hz at 720p with the use of frame packing (currently used in HD3D) and it can use 1080p. Just not at the same time as far as I am aware.
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May 4, 2012 5:48:56 AM

JoshDBoyle said:


The TV is 1080p and 120hz refresh rate...


120Hz monitors and 120HZ HDTVs do not operate the same way.

A 120Hz monitor accepts 120Hz input thru dual-DVI (each DVI operates at 60Hz), HDMI 1.4a or DisplayPort.

A 120Hz HDTV is very different. HDTVs only accepts 60Hz input so they only receive at most 60 frames per second. The "120Hz" has to do with video processing. Simply stated, when the HDTV is set to 120Hz mode it basically creates an interpolated frame between every two actual frames. This is done to smooth out video playback. This also creates a bit of lag (which is bad for games) because it takes time to create and insert every interpolated frame. 240Hz HDTVs does even more video processing which means increased input lag.
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May 4, 2012 10:54:02 PM

The TV itself may refresh at 120Hz, but it isn't capable of accepting a 120Hz signal via HDMI.

This is a limitation of the HDMI chip that is being used. Chips with the requisite speed to support 1080p120 or even formats like frame packed 1080p60 for 3D content (60 fps per eye) were only released recently and are only beginning to trickle into hardware.

For example, here is a press release for a 300Mhz chip that was introduced in May 2011 - as you can imagine it takes time for such technology to become commonplace.

http://www.siliconimage.com/news/releasedetails.aspx?id...

Your video card is the second limitation. The Radeon 7970 was the first video card to support such formats over HDMI.
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