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VGA cord bandwidth + Refresh rate Question

post #1 of 16
Thread Starter 
Hey guys!!!!!!!!!!!!!!!!

Ok, so my acer monitor only has a VGA out and 2 HDMI outs.
http://www.newegg.com/Product/Product.aspx?Item=N82E16824009315

Question:

The screen is good upto 75Hz refresh rate. Games are sooooo much smoother. However, I've experienced ALOT of screen taring and it almost looks like the screen when pitching left and right, has waves going up objects and textures with what I see. I can obviously visually see that there's a sort of broken link between areas of my screen, its where the same part of the screen doesn't line up and it moves up to the top of my screen. It's hard to explain.
It looks like this but it goes up to the top of my screen like a wave:
537

I feel its the VGA cable that I'm using that's causing this problem. I've got my refresh rate down to 70hz and it seems like its alot better but even at 60hz it does this screen taring. My video card is a DVI out so I'm going from a dual link DVI out to VGA adapter, then VGA cord to the monitor.

Is it the frame limiter that I have my game set to? Right now I play bf3 and with a frame limiter, its set to 70hz refresh rate, 72frame limit which in the game I see 71.9fps....

Thanks guys! It's not horribly noticeable when I play but I do get pretty bad headaches if I play for longer then 2hrs so I'm trying to figure out why that's the case... I do take breaks and look at far objects to use the other muscles in my eyes...but yea....lol

Thanks!
post #2 of 16
personally, I would get a DVI to HDMI cable, and hook up your monitor that way. It will give you better quality, as it does have more bandwidth than VGA and more resistant to noise. I had my monitor hooked up via VGA when I used my onboard graphics, before I got a card, and I used to get horizontal ghosting stripes (sorry, its the best way I can explain it), but this was fully cured when I moved to DVI on my new card,

As for the screen tearing, I do not think that is related to your VGA connection, and is more a software setting. Have you tried switching on your Vsync in your drivers? I *think* it may have something to do with that, but i'm not sure. Somebody with more experience of tearing may be able to help you here. smile.gif

L x
post #3 of 16
Inputs. Your monitor has INputs, not outputs.
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post #4 of 16
It's not the cable, it's the difference between your GPU's outputted frames and your monitor's refresh rate not being perfectly synchronized. This is why most games have a "vsync" option--which helps to alleviate screen tearing most of the time.

Read this, it explains it.
    
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post #5 of 16
Thread Starter 
Ok well I don't have Vsync on, I have a frame limiter which IMO is much better.... I don't get drastic drops like you would with Vsync or input lag from the mouse...

So its not the DVI to VGA then VGA into the monitor? It's got something to do with the software? I turned on triple-buffering. Now is 72fps cap not good for a 70hz refresh rate?
post #6 of 16
Try HDMI, that may fix it. Or try dropping your rate limiter to 70fps, or maybe even 69.
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post #7 of 16
Quote:
Originally Posted by Cakewalk_S View Post

Ok well I don't have Vsync on, I have a frame limiter which IMO is much better.... I don't get drastic drops like you would with Vsync or input lag from the mouse...
So its not the DVI to VGA then VGA into the monitor? It's got something to do with the software? I turned on triple-buffering. Now is 72fps cap not good for a 70hz refresh rate?

Did you even click on the link I pasted and read it? It explains your situation exactly. It has nothing to do with the inputs--this happens over any input. It has nothing to do with the specific software either. It has to do with the difference between your monitor's refresh rate and how many fps your gpu can output and synchronicity between them. Even if your constant fps output from your gpu matches your monitor's refresh rate exactly, you can still have problems because they are not perfectly matched. FPS caps do not fix this. Here is the info:
Quote:
Originally Posted by http://hardforum.com/showpost.php?s=bb7d68819d5c02ab4f5c87d21232986f&p=1027966611&postcount=1 
Now this is where the common misconception comes in. Some people think that the solution to this problem is to simply create an FPS cap equal to the refresh rate. So long as the video card doesn't go faster than 75 FPS, everything is fine, right? Wrong.

Before I explain why, let me talk about double-buffering. Double-buffering is a technique that mitigates the tearing problem somewhat, but not entirely. Basically you have a frame buffer and a back buffer. Whenever the monitor grabs a frame to refresh with, it pulls it from the frame buffer. The video card draws new frames in the back buffer, then copies it to the frame buffer when it's done. However the copy operation still takes time, so if the monitor refreshes in the middle of the copy operation, it will still have a torn image.

VSync solves this problem by creating a rule that says the back buffer can't copy to the frame buffer until right after the monitor refreshes. With a framerate higher than the refresh rate, this is fine. The back buffer is filled with a frame, the system waits, and after the refresh, the back buffer is copied to the frame buffer and a new frame is drawn in the back buffer, effectively capping your framerate at the refresh rate.

That's all well and good, but now let's look at a different example. Let's say you're playing the sequel to your favorite game, which has better graphics. You're at 75Hz refresh rate still, but now you're only getting 50FPS, 33% slower than the refresh rate. That means every time the monitor updates the screen, the video card draws 2/3 of the next frame. So lets track how this works. The monitor just refreshed, and frame 1 is copied into the frame buffer. 2/3 of frame 2 gets drawn in the back buffer, and the monitor refreshes again. It grabs frame 1 from the frame buffer for the first time. Now the video card finishes the last third of frame 2, but it has to wait, because it can't update until right after a refresh. The monitor refreshes, grabbing frame 1 the second time, and frame 2 is put in the frame buffer. The video card draws 2/3 of frame 3 in the back buffer, and a refresh happens, grabbing frame 2 for the first time. The last third of frame 3 is draw, and again we must wait for the refresh, and when it happens, frame 2 is grabbed for the second time, and frame 3 is copied in. We went through 4 refresh cycles but only 2 frames were drawn. At a refresh rate of 75Hz, that means we'll see 37.5FPS. That's noticeably less than 50FPS which the video card is capable of. This happens because the video card is forced to waste time after finishing a frame in the back buffer as it can't copy it out and it has nowhere else to draw frames.

Essentially this means that with double-buffered VSync, the framerate can only be equal to a discrete set of values equal to Refresh / N where N is some positive integer. That means if you're talking about 60Hz refresh rate, the only framerates you can get are 60, 30, 20, 15, 12, 10, etc etc. You can see the big gap between 60 and 30 there. Any framerate between 60 and 30 your video card would normally put out would get dropped to 30.

Now maybe you can see why people loathe it. Let's go back to the original example. You're playing your favorite game at 75Hz refresh and 100FPS. You turn VSync on, and the game limits you to 75FPS. No problem, right? Fixed the tearing issue, it looks better. You get to an area that's particularly graphically intensive, an area that would drop your FPS down to about 60 without VSync. Now your card cannot do the 75FPS it was doing before, and since VSync is on, it has to do the next highest one on the list, which is 37.5FPS. So now your game which was running at 75FPS just halved it's framerate to 37.5 instantly. Whether or not you find 37.5FPS smooth doesn't change the fact that the framerate just cut in half suddenly, which you would notice. This is what people hate about it.

If you're playing a game that has a framerate that routinely stays above your refresh rate, then VSync will generally be a good thing. However if it's a game that moves above and below it, then VSync can become annoying. Even worse, if the game plays at an FPS that is just below the refresh rate (say you get 65FPS most of the time on a refresh rate of 75Hz), the video card will have to settle for putting out much less FPS than it could (37.5FPS in that instance). This second example is where the percieved drop in performance comes in. It looks like VSync just killed your framerate. It did, technically, but it isn't because it's a graphically intensive operation. It's simply the way it works.

All hope is not lost however. There is a technique called triple-buffering that solves this VSync problem. Lets go back to our 50FPS, 75Hz example. Frame 1 is in the frame buffer, and 2/3 of frame 2 are drawn in the back buffer. The refresh happens and frame 1 is grabbed for the first time. The last third of frame 2 are drawn in the back buffer, and the first third of frame 3 is drawn in the second back buffer (hence the term triple-buffering). The refresh happens, frame 1 is grabbed for the second time, and frame 2 is copied into the frame buffer and the first part of frame 3 into the back buffer. The last 2/3 of frame 3 are drawn in the back buffer, the refresh happens, frame 2 is grabbed for the first time, and frame 3 is copied to the frame buffer. The process starts over. This time we still got 2 frames, but in only 3 refresh cycles. That's 2/3 of the refresh rate, which is 50FPS, exactly what we would have gotten without it. Triple-buffering essentially gives the video card someplace to keep doing work while it waits to transfer the back buffer to the frame buffer, so it doesn't have to waste time. Unfortunately, triple-buffering isn't available in every game, and in fact it isn't too common. It also can cost a little performance to utilize, as it requires extra VRAM for the buffers, and time spent copying all of them around. However, triple-buffered VSync really is the key to the best experience as you eliminate tearing without the downsides of normal VSync (unless you consider the fact that your FPS is capped a downside... which is silly because you can't see an FPS higher than your refresh anyway).

Edited by guyladouche - 4/7/12 at 7:49am
    
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post #8 of 16
Thread Starter 
Yea I read it, triple buffering is on but I still get bad screen taring.... I've tested fps locks with a 75hz refresh @ 74fps cap, 75, 76,77,78fps and all of them I get screen taring....
post #9 of 16
Thread Starter 
Does it have anything to do with the DVI link and the VGA? Dual/Single?

I have both these connectors. My GPU came with this one:
430

and I have an extra one like this:
406

To my understanding the top one is single link and the other is dual. I heard there's no difference between the two except at really high resolutions...

I tried both and it didn't really do anything different. Still screen taring...
post #10 of 16
No...it's not the cable. Screen tearing has nothing to do with the cable used. The cable has nothing to do with screen tearing. It's caused by the phenomenon in the post I linked to. That's it.

The best you can do is disable any artificial FPS caps (this works against you if you're encountering screen tearing because it is one more mis-match between the frames your graphics card is rendering and what is actually sent to the display from the frame buffer), enable v-sync, and enable tripple-buffering if it's an option in the game. The cable has no effect.
    
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