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How exactly is crossfire broken?

post #1 of 5
Thread Starter 
I've been wondering for awhile after reading how Xfire is really bad and all: how exactly is it bad? Like, does it scale horribly with 2 cards, or whats the problem that makes it virtually unusable?
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post #2 of 5
there is an issue with what is called "micro stutter"

what happens in cross fire is the cards take turns rendering frames, so when the second card renders a frame it has to be decoded/sent out to the primary card to be displayed. there are timing issues where that frame takes too long to get sent out to the primary card/monitor causing a jittery effect that is visualy unappealing, even if your framerates are really high.

there is supposed to be a driver fix coming in the next month, so we will see what AMD has to offer by then
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post #3 of 5
Thread Starter 
Quote:
Originally Posted by AlaskaFox View Post

there is an issue with what is called "micro stutter"

what happens in cross fire is the cards take turns rendering frames, so when the second card renders a frame it has to be decoded/sent out to the primary card to be displayed. there are timing issues where that frame takes too long to get sent out to the primary card/monitor causing a jittery effect that is visualy unappealing, even if your framerates are really high.

there is supposed to be a driver fix coming in the next month, so we will see what AMD has to offer by then
Thanks for the awesome answer! +Rep!
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post #4 of 5
Frame times crash course incoming!

Warning: Spoiler! (Click to show)
Quote:
Originally Posted by Alatar View Post

Look here's a crash course on frame times:

Let's take two GPU setups that have similar average fps. Say 100 fps both on average.


The Nvidia setup:
100 average fps
10ms average frame time



The AMD setup:
100 average fps
10ms average frame time

But now the difference is this:

The AMD setup has a bunch of 0ms frames. you cannot see these frames due to them lasting 0ms. Even though these frames contribute to the average frame time / fps number they do not do anything to the gaming experience.

This brown line is what reviews will have you believe is the gaming experience:



Here are the frames that need to be removed due to you not seeing them:



Here the blue represents the actual frame times that you can see:



And this brown line is the final real life average frame time / frame rate that you're left with:



And them compare to the brown real life line on the Nvidia side:



You will get a real life experience of 100fps with the nvidia setup and 50fps with the amd setup. Saying you can't see the difference proves nothing but that you cannot distinguish the difference between 100 and 50fps.
 
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post #5 of 5
Well Played Alatar, Well Played.
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