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View Full Version : CPU bottleneck when does it stop?


Pandora's Box
08-14-04, 04:02 PM
Over in this thread: http://www.nvnews.net/vbulletin/showthread.php?t=34683

there was a debate going about the new athlon 64's and if there is a fps difference at high resolutions with aa and af applied when comparing it to an athlon xp cpu.

My opinion is that if the resolution and aa and af are set high then the gpu becomes the bottleneck and you would get around the same fps whether your running a high end athlon xp or athlon 64. what do you guys think?

Ofcourse we are referring to Geforce 6800 GT and Ultras here

MUYA
08-14-04, 04:06 PM
hmm yeah dude, I misread anandtech's article with respect to GPU performance with CPU. Seems anadtech didn't turn on teh AA i their article. However, I have noticed ppl getting better fps at 1280 by 1024 with 4xAA and 8X af (high quality settings) with athlon64 CPUs. have to hunt for more benches when I have the time.

Mojoe
08-14-04, 04:11 PM
In the newest games my fps is the same up to 1280x1024 with 4aa and 8xaf, at 1600x1200 it takes a deep dive.

Pandora's Box
08-14-04, 04:17 PM
In the newest games my fps is the same up to 1280x1024 with 4aa and 8xaf, at 1600x1200 it takes a deep dive.


ofcourse it does. not what we are talking about here. we are talking about whether the fps is the same on an athlon 64 system to an athlon xp high end cpu. at the same aa and af levels (around 4xaa 8xaf 1280x1024 and up res)

jAkUp
08-14-04, 04:29 PM
Yes it does matter that it takes a deep dive. That is showing that it is becoming a GPU bottleneck. And yes, at high resolutions, AA and AF, the video card will ALWAYS be the bottleneck since those don't use any CPU cycles. At high resolutions with AA/AF. Im talking like 1600x1200 4x/8x, you will see a bigger increase if you OC your video card.

Pandora's Box
08-14-04, 04:33 PM
Yes it does matter that it takes a deep dive. That is showing that it is becoming a GPU bottleneck. And yes, at high resolutions, AA and AF, the video card will ALWAYS be the bottleneck since those don't use any CPU cycles.


ok but what the question is, is these dives in fps. are they affected by cpu speed? Guess what we are trying to determine is if theres any difference in gaming at the resolutions we play at (1280x1024 or higher with 4xaa 8xaf) does the cpu speed affect fps?

I wouldnt think so since at that res and aa af modes your totally GPU dependent.

Nutty
08-14-04, 05:10 PM
The cpu will always have some impact on performance, because games aren't totally 100% parallel processing on cpu and gpu. There wont be much difference in heavily gpu bottlenecked situations tho.

odin20
08-14-04, 05:22 PM
Dave i agreed with you in the other post and i do now too but at a certain point you will definitely need a faster cpu. Basically if you cannot get 40 fps at 800 * 600 in doom3 with your current cpu then you will not with a faster Video card. A faster video card gives you a maximum you can get before you lose fps to gpu cycles. For example a 6800 ultra at 1280 * 1024 can go up to 4xaa and 8xaf at 70fps before it starts to lose cycles because of the gpu. But a lesser cpu will already be at 20 or 30 fps regardless of gpu so yeah you will be at the same aa and af level and even resolution but one guy is at 60 fps and the other is at 20 or 30 which is all his cpu can handle. In other words the guy with the faster cpu has more room to turn things up(image quality) till he starts losing frames. Another situation is online games. Most of them are cpu dependant not gpu(video card) dependant because of all the characters on screen at once. Planetside is a good example. When i play it i play at very high resolution and very high aa and af. But no matter what i do when there is alot of people around my frames dive into the 30's whether im at 800 * 600 or 1600 * 1200. A better card just makes it look prettier. But a faster cpu would prolly help more in games such as this.
I know im saying a bit of the opposite that i did in the other thread but its just important to realize that nothing is cut and dry. You must have a decent cpu to feed a modern card but a 3 ghz cpu is in no way cpu bound in most new games at high rez with aa and af. Websites just like to say crap like "wow we couldnt feed this x800xt enough power the cpu couldnt keep up" meanwhile they had the resolution at 1280 * 1024 with no aa or af and it was a old game. You can make anything look the way you want.