Crossfire Bottleneck 2.0 x16 & 2.0 x4

[Durvelle27]

How much of a bottleneck will i have by using 2x 2.0 x16 Slots @x16 & x4 ? thx

[cadaveca]

from 5% to 50%, with 6950's. Depends on the game. Most are closer to that 5%.

[Durvelle27]

Originally Posted by cadaveca

from 5% to 50%, with 6950's. Depends on the game. Most are closer to that 5%.

50% that's alot

i found this

http://www.techpowerup.com/reviews/I...caling/23.html

[cadaveca]

That's just single cards. Multi-GPU is a bit different, too. YOu cna see the 680 loses like 15% at times on it's own, never mind having to communicate with another card.

8x8 tohugh, doesn't seem to matter to much, and sometimes is faster than x16/x16. I dunno WTF is up with THAT. Probably a driver-related thing.

[Durvelle27]

how much will i see. i play Battlefield 3, Sleeping Dogs, Batman AC, NBA 2K12 Call of Duty MW2, MW3, Black OPs, Skyrim, Max Payne 3

Edit: i got a new mobo because the one i currently have doesn't support cpus over 95W, Sata 6GBs, USB 3.0. so the one i got which is a ASUS M5A97 EVO has everything i wanted plus an additional PCIe slot which i thought i could use to increase my gaming experience on my 1920x1080 monitor

[cadaveca]

Originally Posted by Durvelle27

ASUS M5A97 EVO

I had one of those. Not a bad board.

with 6950's, and Tri-Fire benchamrking, use Catalyst 12.3 with 12.3 app profile, or 11.11c "performance" driver.


I'm using the 12.8's with the most recent app profile for BF3 every day, and they are not capable of playing @ 2560x1600 on ultra, at all. In fact, just 2650x1600 is near impossible iwth many titles. 1920x1080 is OK, 1920x1200 sees some slowdowns.

I had as many as 4x 2 GB 6950's, testing, was not overly impressed with it, to be honest, and I ran with 1100T, 8150, 2600K, 3770K, 3960X, 3820, with PCIe configs from x16/x4/ all the way up to x16/x16/x16/x16.

Fortunately, it only takes a quick load of BF3 to find out that the 4th card was basically useless, so I got rid of it, and kept 3.

[Durvelle27]

i use 12.8 right now so if i crossfire it would be better to use 12.3

[brandonwh64]

I have the two 6950's with 12.8 and no caps as it runs BF3 on ultra settings maxed 60FPS steady. One thing you will have to take into account is that I have sandybridge at 4.5ghz

[Durvelle27]

also found this

http://www.tomshardware.com/reviews/...e,2887-10.html

@brandonwh64 your board also runs at dual x8/x8

[brandonwh64]

Originally Posted by Durvelle27

@brandonwh64 your board also runs at dual x8/x8

Yes it does, I believe 1155 will only do that

[Durvelle27]

Originally Posted by brandonwh64

Yes it does, I believe 1155 will only do that

see mines run at x16/x4

[cadaveca]

Originally Posted by brandonwh64

I have the two 6950's with 12.8 and no caps as it runs BF3 on ultra settings maxed 60FPS steady. One thing you will have to take into account is that I have sandybridge at 4.5ghz

@ 1080P. .


And yeah, Brandon has my 4th GPU.

[brandonwh64]

Originally Posted by cadaveca

@ 1080P. .


And yeah, Brandon has my 4th GPU.

Yep 1080P for me

[erocker]

Originally Posted by Durvelle27

see mines run at x16/x4

Not an optimal setup. I've seen quite a few that have problems running CrossFire with this configuration, however those that don't have problems generally don't post about it.

[cadaveca]

Originally Posted by erocker

however those that don't have problems generally don't post about it.

Sub-optimal performance isn't nessecarily a problem. It also leads to forced power savings.

[cdawall]

2.0 X4 is just as fast as 1.0 X8 which was a widely used standard on a lot of boards. Might loose some performance, but I would assume the performance gains of 2 cards out weighs that a bit...

[cadaveca]

Originally Posted by cdawall

2.0 X4 is just as fast as 1.0 X8 which was a widely used standard on a lot of boards. Might loose some performance, but I would assume the performance gains of 2 cards out weighs that a bit...

I'm pretty sure I read an interview with some ATI dude that stated that it wasn't just about bandwidth, but also the number of lanes, as although 4 lanes could feasibly be enough, the card in that x4 slot still needs to use some of those 4 lanes to communicate with the other card, making that overall bandwidth figures meaningless.

To prove this, you smiply need test with PCIe 3.0 vs PCIe 2.0, and look for linear performance losses based on lanes, rather than the bandwidth. And guess how that works out on PCIe 3.0...?

[cdawall]

Originally Posted by cadaveca

I'm pretty sure I read an interview with some ATI dude that stated that it wasn't just about bandwidth, but also the number of lanes, as although 4 lanes could feasibly be enough, the card in that x4 slot still needs to use some of those 4 lanes to communicate with the other card, making that overall bandwidth figures meaningless.

To prove this, you smiply need test with PCIe 3.0 vs PCIe 2.0, and look for linear performance losses based on lanes, rather than the bandwidth. And guess how that works out on PCIe 3.0...?

Good call...

[cadaveca]

Originally Posted by cdawall

Good call...

Don't get me wrong...I don't REALLY understand how this al lworks..I just know what I've been told, and what the test results give me.


I tell you, trying to find decent Eyefinity performance has lead to some interesting performance testing.

[erocker]

Originally Posted by cadaveca

Sub-optimal performance isn't nessecarily a problem. It also leads to forced power savings.

From issues I've seen it also leads to CrossFire not working correctly. I'm thinking some sort of sync issues... or something. Like I said though, it's possible there may be no problem at all.

[Durvelle27]

so is it worth it as i can get another HD 6950 2GB cheap and also i want be going pas 1080p anytime soon

[cadaveca]

Originally Posted by erocker

From issues I've seen it also leads to CrossFire not working correctly. I'm thinking some sort of sync issues... or something. Like I said though, it's possible there may be no problem at all.

I've run into that, but I cannot say that I saw it in BF3. Some much software cna change things, I think it's probably something that happens on an individual basis, kinda like Realtek drivers taknig a crap on many systems.


Codemasters titles seem the most sensitive to the lane change, and Source games for sync issues, kinda basic stuff, some of it I am sure could be dealt with by drivers, perhaps, but I don't think that AMD really intends for such configurations to have high-performance graphics cards.

I'll ahve to check out how the 8150 reacts, jsut got the OS installed this morning. I've decided I want to get the most performance possible for the least amount of power, but still be able to play BF3 @ 1920x1080. Then I want to make it as small as is possible.

[Durvelle27]

???

[cadaveca]

Will it be faster, FPS-wise?

YES.

Will there be a bottleneck with x16/x4?

YES.

Is there a potential for problems?

YES.

Is it worth it?

I dunno. If you had a x8/x8 motherboard, I'd say sure, no question.

If you are willing to deal with potential issues, then sure, it's worth it. I'd make plans ofr a motherboard upgrade part of that though, but personally, I see it as a worthy expense. There are many affordable x8/x8 boards out there, and I know you cna get 6950's for very little as well.

Do both, for less than $200, and yeah, i think it's worth it. You'll get near double the FPS @ x8/x8, nvidia, or AMD. Dual-GPU usually works pretty good now.

[Durvelle27]

well when i got my mobo i got it an a FX 8120 for $150