Understanding refresh rates at non native resolutions

[Flowerbridge]

Hi,

I have a 1900 x 1200 monitor that runs at 60hz at its native resolution. I've been having issues with being "capped at 60fps," so before I wanted to save $$ on an expsensive 120hz monitor.

I read that the monitor runs at 75hz at 1260x900? or something like that. When I tested it in-game at that resolution, my in-game FPS (BFBC2) ran like complete shit, like 30-40fps, even lower than at my normal resolution.

Am I missing something or does this not seem right?


Have an overclocked E8400 at 3.8ghz and a 1gb radeon 4870. 6 gigs of ram

 

[cmay119]

Did you turn up the eye-candy (AA, AF, etc) to compensate for lowering the resolution? 1280x800 is less than half of the resolution of 1920x1200 (1.024 megapixels vs 2.304 megapixels), if the eye candy isn't turned on, there isn't enough load to put onto the video card. This results in the work being put onto the CPU instead. Which is not able to render 3d as efficiently as the video card. Hence why you're seeing a drop in frame-rates instead of a jump.

Try turning up all the settings besides resolution and see if your frames go up as well. Hope that helps.

 

[Gorankar]

^^^Huh^^^

 

[cmay119]

^^^Huh^^^

It causes a bottleneck is what I meant to say. Essentially lowering performance instead of the intended raising of performance. I've read of this happening multiple times, I'll try to find some articles on the subject, I'm sure they'll word it a lot better than I did.

Here's a quote from a member over @ toms, explaining a little bit better what I mean:

Ok i will try and explain it but a lot of people even those who claim to know every thing dont seem to under stand it.
There is a possability that you are causing an artificial CPU bottleneck by using such a low resolution.
Its a lot easier if you just try it at a higher res and see if it makes a differance but the theory behind the sugestion goes like this.
Running at a lower resolution gives the GPU a lot les to do as it has less dots/pixels to draw, its a bit more involved than that but im trying to keep it simple. The CPU still has the same work load regardless of the resolution so by giving the GPU less to do you are giving the CPU less time in effect to do what it needs to do.
Say for example the CPU can generate the information the GPU needs to render the frames at a rate that equates to 60FPS at 1680x1050 and your GPU can render frames at 55 FPS at that resolution then all is fine as the GPU isnt waiting on info to do its job.
If you reduce your resolution to 1024x768 then it should be clear to all that the GPU can render that faster than it could at 1680x1050.
Where you get the problem is if you are asking the CPU which can render at 60FPS to now try and keep up with your GPU which because its not drawing so many Pixels can run at 75FPS then its restricted to what the CPU can deliver.
Its not as black and white as it will now just render at 60 FPS as the bottleneck causes issues which make the card skip frames etc to try and keep up and you get a cumalitive effect which means what you actuially see is less than the CPU max.
It gets worse if you have V-sync on (please tell me you dont) as this will run to multiples or intrergers of 60 which could end up reducing your actual FPS by a quarter or even a half.

From this thread:
http://www.tomshardware.com/forum/279585-33-bottleneck

I'm having troubles finding a true article on the subject, however.

EDIT: In all fairness, I can't vouch for this myself, as I don't run games at anything besides native resolution. Just give it a try. If it helps, then the theory holds merit.

 

[Flowerbridge]

Thank you very much, I'll try this out tonight.

Did you turn up the eye-candy (AA, AF, etc) to compensate for lowering the resolution? 1280x800 is less than half of the resolution of 1920x1200 (1.024 megapixels vs 2.304 megapixels), if the eye candy isn't turned on, there isn't enough load to put onto the video card. This results in the work being put onto the CPU instead. Which is not able to render 3d as efficiently as the video card. Hence why you're seeing a drop in frame-rates instead of a jump.

Try turning up all the settings besides resolution and see if your frames go up as well. Hope that helps.