Theres some new leaked Catalyst drivers out. I wonder if they fix the micro stuttering issue...
http://www.station-drivers.com/page/ati%20catalyst.htm
Printable View
Theres some new leaked Catalyst drivers out. I wonder if they fix the micro stuttering issue...
http://www.station-drivers.com/page/ati%20catalyst.htm
Those do fix the stutters, at least for me in Crysis.
saaya
that's a bummer, but im sorta grateful that there is another reason NOT to double up on gcards.Quote:
it affects sli AND xfire, it happens in ALL games...
its just more apparent in some games compared to others...
i would really like the sli/cf thing to work well, but i found it to be flawed, surely there are circumstances where sli and cf work flawlessly?
yes, with sfr and tile mode there should be less stuttering.
especially with tile mode, cause with tile mode, in theory, you can always split the frame in 50% and 50% of the work that needs to be done and each gpu can then finish rendering its tiles in the same time. this should assure a constant frametime. and also! the gpus work on the same frames together, making it virtually appear as one gpu to the game! so there wont be any game time or frame time issues caused by splitting up the work and distributing it amongst several gpus. this technique is especially interesting because a single gpu already works that way in some regards.
afaik ati gpus internally break down each frame into tiles of 8x8 or 16x16 pixels iirc, nvidia gpus instead break down each frame into rectangular horizontal stripes of 20x2 pixels or something like that, and then each part of the gpu is then working on such a chunk of data.
so tile mode would basically mean extending this technique to several gpus. unfortunately it seems its not easy to master and get it working right with a high latency and limited bandwidth link between the gpus.
gpus have a massive bandwidth to their memory of 150gb/s, but dont forget, the internal bandwidth between all the parts of a gpu is way beyond that!
getting both gpus to work as one would either require a massive bus link, and even then youd have a latency impact, or, you need to find a way to share as little data as possible and compress data as good as they can. compressing data and managing huge amounts of data is one of the most important things in gpu tech afaik. there are rumors that with Rv7xx there will be some fast connection between the gpus.
Im thinking they might share some of the memory, which basically means they use a part of the memory controller to create a link between both gpus.
Again, modern gpus have a mem bandwidth of up to 150gb/s and they use 8 memory chips, so thats 18gb/s per chip roughly.
If they share one of the 8 chips, then this would be as fast as having 16 pciE lanes only for both gpus to talk to each other...
and since the memory controllers are connected indirectly, this might even be more effcient, since the gpu can probably access and work with data faster if its already in the memory compared to receiving it through the pciE interface and then loading it to memory.
anyways, im drifting off topic :D
seraphiel, i know what you mean, why is adding frames a bad thing, it wont be as good as having 2x the original frames cause of the issues, but it should still be better than having only frames from one card. well, your right... but... it seems having a constant frametime seems to be more important than a high frame rate.
and im starting to think that the real issues people are seeing here are actually caused by the gametime delays from one frame to the other.
there is always a delay from the time a gpu starts to work on a new frame, and basically works on that snapshot of that game time, until its finished and then displayed. it seems that if you use certain post processing effects or a game is programmed in a certain way, then one gpu needs longer from snapshot of the gametime until it finished the frame.
maybe in some games or scenarios you always need to base the next frame on the previous one for some special effects? and to speed this up, ati and nvidia maybe do it like this: gpu1 renders one frame after the other recycling its own frames, gpu2 always recycles the frames from gpu1 to create the next frame.
and as a result the frame times and game times are not matching anymore?
that would actually be a different issue than what i previously explained, but it would describe the issues people are seeing here much better.
as it seems to be limited to only some games and stuttering a lot more and... rougher, than what youd expect from real micro stuttering based on inconsistent frame times alone