Overclock.net banner

1 - 15 of 15 Posts

·
AMD Overclocker
Joined
·
9,178 Posts
Discussion Starter · #1 ·
Hey guys, I have been wondering lately since I have only tried crossfire so far is there any real difference in the way they are done? Is one more stable than the other or I guess more "smooth"?
 

·
Registered
Joined
·
2,962 Posts
Before 4xx it seemed as if CF was slightly better, scaling wise and stability wise, but now with the 4xx I don't know, I think SLI is slightly better now. Either way, the differences in performance are very small.
 

·
Premium Member
Joined
·
14,732 Posts
The nice thing about Crossfire is that you can run both cards at their maximum overclock. Since it's highly unlikely that 2 cards would max at the same speed, it allows you to squeeze every bit of performance out of your system.
 

·
AMD Overclocker
Joined
·
9,178 Posts
Discussion Starter · #4 ·
Quote:


Originally Posted by Xenthos
View Post

Before 4xx it seemed as if CF was slightly better, scaling wise and stability wise, but now with the 4xx I don't know, I think SLI is slightly better now. Either way, the differences in performance are very small.

Yeah, I heard the 4xx series was pretty good scaling wise. Some ati cards are also very good scaling wise as well though, like my 4770's


Quote:


Originally Posted by sccr64472
View Post

The nice thing about Crossfire is that you can run both cards at their maximum overclock. Since it's highly unlikely that 2 cards would max at the same speed, it allows you to squeeze every bit of performance out of your system.

And sli doesn't allow you to oc your cards or what? What do you mean by maximum oc? Do you mean it allows both cards to be run at different clock speeds and not have them have to be equal?
 

·
Premium Member
Joined
·
36,139 Posts
I think (could be wrong) that SLi has 1 more rendering mode than Crossfire does.

But to my knowledge, Crossfire & SLi both have two rendernig modes in Common

  • Split Frame Rendering (SFR), the first rendering method. This analyzes the rendered image in order to split the workload 50/50 between the two GPUs. To do this, the frame is split horizontally in varying ratios depending on geometry. For example, in a scene where the top half of the frame is mostly empty sky, the dividing line will lower, balancing geometry workload between the two GPUs. This method does not scale geometry or work as well as AFR, however.
  • Alternate Frame Rendering (AFR), the second rendering method. Here, each GPU renders entire frames in sequence - one GPU processes even frames, and the second processes odd frames, one after the other. When the slave card finishes work on a frame (or part of a frame) the results are sent via the SLI bridge to the master card, which then outputs the completed frames. Ideally, this would result in the rendering time being cut in half, and thus performance from the video cards would double. In their advertising, Nvidia claims up to 1.9x the performance of one card with the dual-card setup.
SFR is called Scissor Rendering by ATi.

And SLi's unique rendering mode is: (EDIT: ATi has a version this mode as well under the name AA & HDR Rendering)

Quote:


SLI Antialiasing. This is a standalone rendering mode that offers up to double the antialiasing performance by splitting the antialiasing workload between the two graphics cards, offering superior image quality. One GPU performs an antialiasing pattern which is slightly offset to the usual pattern (for example, slightly up and to the right), and the second GPU uses a pattern offset by an equal amount in the opposite direction (down and to the left). Compositing both the results gives higher image quality than is normally possible. This mode is not intended for higher frame rates, and can actually lower performance, but is instead intended for games which are not GPU-bound, offering a clearer image in place of better performance. When enabled, SLI Antialiasing offers advanced antialiasing options: SLI 8X, SLI 16X, and SLI 32x (8800-series only). A Quad SLI system is capable of up to SLI 64X antialiasing.

Though, AFR in both SLi & Crossfire gives way to Micro-stutter. To varying degree's though.

EDIT: Apparently I'm wrong.

ATi Crossfire has 4 Rendering Modes outlined here. Which means SLi has one less rendering mode
 

·
Premium Member
Joined
·
36,139 Posts
Quote:


Originally Posted by Behemoth777
View Post

And sli doesn't allow you to oc your cards or what? What do you mean by maximum oc? Do you mean it allows both cards to be run at different clock speeds and not have them have to be equal?

In SLi both cards need the same overclock.

WHile in Crossfire one card can be 1000mhz/1400mhz with the other card being 900mhz/1300mhz

And it doesn't matter which one is Primary and which one is the Slave.

Also, Crossfire allows you to Mix & Match GPU's of the same core.

IE: HD5970, HD5870, HD5850, & HD5830 can all Crossfire together in any combination adding up to 4 cards.

Technically, CFX allows for a total of 8 cards using 4 x (x2) cards, but this is not supported by drivers yet. Just the CFX Design.
 

·
AMD Overclocker
Joined
·
9,178 Posts
Discussion Starter · #7 ·
Quote:


Originally Posted by Tator Tot
View Post

I think (could be wrong) that SLi has 1 more rendering mode than Crossfire does.

But to my knowledge, Crossfire & SLi both have two rendernig modes in Common

  • Split Frame Rendering (SFR), the first rendering method. This analyzes the rendered image in order to split the workload 50/50 between the two GPUs. To do this, the frame is split horizontally in varying ratios depending on geometry. For example, in a scene where the top half of the frame is mostly empty sky, the dividing line will lower, balancing geometry workload between the two GPUs. This method does not scale geometry or work as well as AFR, however.
  • Alternate Frame Rendering (AFR), the second rendering method. Here, each GPU renders entire frames in sequence â€" one GPU processes even frames, and the second processes odd frames, one after the other. When the slave card finishes work on a frame (or part of a frame) the results are sent via the SLI bridge to the master card, which then outputs the completed frames. Ideally, this would result in the rendering time being cut in half, and thus performance from the video cards would double. In their advertising, Nvidia claims up to 1.9x the performance of one card with the dual-card setup.
SFR is called Scissor Rendering by ATi.

And SLi's unique rendering mode is: (EDIT: ATi has a version this mode as well under the name AA & HDR Rendering)
Though, AFR in both SLi & Crossfire gives way to Micro-stutter. To varying degree's though.

EDIT: Apparently I'm wrong.

ATi Crossfire has 4 Rendering Modes outlined here. Which means SLi has one less rendering mode

Which would you say has a higher tendency to succumb to microstutter?
 

·
Registered
Joined
·
401 Posts
No fanboyish **** but the 4XX SLI perfoms better than crossfire, from what im seeing
 

·
AMD Overclocker
Joined
·
9,178 Posts
Discussion Starter · #9 ·
Quote:

Originally Posted by Tator Tot View Post
In SLi both cards need the same overclock.

WHile in Crossfire one card can be 1000mhz/1400mhz with the other card being 900mhz/1300mhz

And it doesn't matter which one is Primary and which one is the Slave.

Also, Crossfire allows you to Mix & Match GPU's of the same core.

IE: HD5970, HD5870, HD5850, & HD5830 can all Crossfire together in any combination adding up to 4 cards.

Technically, CFX allows for a total of 8 cards using 4 x (x2) cards, but this is not supported by drivers yet. Just the CFX Design.
Wow, crossfire is much better in that case then sli. Honestly, it sounds like nvidia needs to catch up to ati. Not in their design, but in the way they implement their gpus.
 

·
AMD Overclocker
Joined
·
9,178 Posts
Discussion Starter · #10 ·
Quote:

Originally Posted by DXcellence718 View Post
No fanboyish **** but the 4XX SLI perfoms better than crossfire, from what im seeing
I've noticed that too. The scaling is pretty remarkable actually. But I still think nvidia needs to rethink the way they implement their gpus. I'm not really a fanboy for either side, I used to own a 9800gtx+ and it was great. I'm starting to more and more lean towards ati though..
 

·
Premium Member
Joined
·
36,139 Posts
Quote:

Originally Posted by Behemoth777 View Post
Which would you say has a higher tendency to succumb to microstutter?
Rendering mode was already pointed out so I assume you mean GPU Brand?

Well, to me, none shows it highly. I've got GTS 250 SLi running & HD5770 CFX Running. Neither has noticable MS.

x2 cards you can notice it though. IE HD5970 CFX or GTX 295 SLi. But that's in a 4 card setup, which is mostly for ePeen since beyond 2 GPU's, neither SLi or CFX scales better.

I've not personally tested it on newer cards, but between the 9800GX2 & HD3870x2, when running a 4 card setup, the ATi version scaled better.
Though, like I said, this has been a bit since I've yet to have a chance to test this on newer cards.

Quote:

Originally Posted by Behemoth777 View Post
Wow, crossfire is much better in that case then sli. Honestly, it sounds like nvidia needs to catch up to ati. Not in their design, but in the way they implement their gpus.
I wouldn't say one is better than the other. They're about on equal playing ground right now. But if nVidia's not careful, ATi will pass them. As ATi's monthly driver release really help out alot.

EVGA does help nVidia in the SLi department with SLi patches though. Which is VERY VERY VERY nice to have, as they enable SLi on newer games that don't have a driver yet.
 

·
Registered
Joined
·
2,612 Posts
I liked my SLI 8800GTS, I could force SLI to work in games that didn't support it, via the Nvidia control panel and SLI profiles(with good results).
I haven't be able to do this with crossfire and I don't know of a way I can, but have only had crossfire for a few months
 

·
Premium Member
Joined
·
36,139 Posts
Quote:

Originally Posted by quakermaas View Post
I liked my SLI 8800GTS, I could force SLI to work in games that didn't support it, via the Nvidia control panel and SLI profiles(with good results).
I haven't be able to do this with crossfire and I don't know of a way I can, but have only had crossfire for a few months
I've not used it, but there's Crossfire Xtension

I think there's a way to do it in the drivers, but I cannot recall. I'm no SLi/CrossfireX expert. But I do know a good amount of info.
 

·
Registered
Joined
·
2,612 Posts
Quote:

Originally Posted by Tator Tot View Post
I've not used it, but there's Crossfire Xtension

I think there's a way to do it in the drivers, but I cannot recall. I'm no SLi/CrossfireX expert. But I do know a good amount of info.
Just the sort of thing I was looking
Will be trying that out over the week or so.
Thanks
 

·
Premium Member
Joined
·
36,139 Posts
Quote:

Originally Posted by quakermaas View Post
Just the sort of thing I was looking
Will be trying that out over the week or so.
Thanks

No prob. I can't really comment on it, since some of the newest games I have were ATi sponsored. And thus didn't need a CFX patch.

Though, it seems basic enough. So it should work fine.
 
1 - 15 of 15 Posts
Top