# Crossfire (PCIE X16 , X4)



## KBeasley (Dec 8, 2010)

I have a Gigabyte 880-GA-UD3H Motherboard. It only has one X16 slot and one X4 slot. I currently have a Gigabyte Radeon HD 6850 and I'm looking to crossfire in time for Battlefield 3.

Would I be better off buying another 6850 and doing crossfire with the X4 slot? Or buying a new motherboard with two X16 slots?


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## MonsterMiata (Jan 5, 2010)

KBeasley said:


> I have a Gigabyte 880-GA-UD3H Motherboard. It only has one X16 slot and one X4 slot. I currently have a Gigabyte Radeon HD 6850 and I'm looking to crossfire in time for Battlefield 3.
> 
> Would I be better off buying another 6850 and doing crossfire with the X4 slot? Or buying a new motherboard with two X16 slots?


You would be better off buying a better gpu like a 6950 or 6970 then swapping mobo's just to x-fire two slower cards that may improve performance. That x4 slot, while can be used for x-fire, will not provide any gains what so ever.

X-fire is not supported by all games and will most of the time cause more headaches then gains. Its a technology that needs a bit more time to mature before its really feasible as its simply not cost effective for the gains you receive.


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## MPR (Aug 28, 2010)

Personally, I would wait and see how the 6850 performs with your new game. I have a 6850 and find that it does quite well with most games. Occasionally I have to tweak a game slightly off its very highest settings but the graphics difference is usually not noticeable.

When running applications _optimized for Crossfire_ two 6850s in Crossfire perform about to the level of a 5970. Since we are approaching the top-end of the video card spectrum here where prices tend to skyrocket, it actually might be more cost effective to add a second 6850 on a new motherboard (total about $375) than it would be to purchase, say a single 5970 at $500. However, as stated above there may be other cheaper single-card options that will allow you to run your game on maximum settings too.

6950 -- $240
6970 -- $350
second 6850 + motherboard -- $375+


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## gcavan (Aug 13, 2009)

I have to disagree. From everything I've read, BF3 should scale very well under Crossfire. I expect a pair of HD 6850's will easily trump a 6950 ($250) and give a 6970 ($350) a good run also. Using an x4 slot on a PCI-e 2.0 motherboard , even with a high end graphics card will not hold back performance by any appreciable amount. 

Here's a test using a pair of GTX 480's in SLI from a year ago.
HARDOCP - GTX 480 SLI x16/x16 vs. x4/x4 - GTX 480 SLI PCIe Bandwidth Perf. - x16/x16 vs. x4/x4


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## MonsterMiata (Jan 5, 2010)

Thats a very interesting find, i was under the impression that that current pci-e cards could not utilize the bandwidth available to them but i was unaware it was that much of a difference.

Gcaven has the right idea if he is correct about scaling. From what i understand however most games do not benefit from a second card as much as a faster single card. This however only applies to games you play so if BF3 scales well then another 480gtx isn't a bad idea provided your psu can provide the juice.


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## Wrench97 (May 10, 2008)

While ATI cards currently do scale up better then Nvidia cards the biggest gain is seen over 1080p resolution as you start to get to 1600p. Early testing in BF3 has yet to show any real gains with either xfire or SLI but keep in mind there have been 0 driver optimizations from either company for the frostbite 2.0 engine and I would not expect to see any until after it's release.
Bottom line if you using 1080p or lower and less then 32" screen size a single 6950 will perform well and run on less power then 2 6850's, Personally I feel a single 6850 will play the game just fine.


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## gcavan (Aug 13, 2009)

Linus from NCIX benchmarked a (IIRC) HD 6970 running it at x16, x8 and x4 bandwidths. The minimal differences were astounding. There is YouTube video of the exercise out there someplace.

Granted, these tests are done using a single monitor config; I expect the results in a high-res, multi-monitor set-up may be somewhat different.

PS: I found it, though I was a bit off on the details. He compares a pair of GTX 580's in SLI at x16/x16 and at x8/x8. He has a bit of trouble reading his calculator, but you get the picture.

LinusTechTips's Channel - YouTube


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## KBeasley (Dec 8, 2010)

Thanks for all the quick responses. I consider myself pretty decent when it comes to hardware knowledge, however I have seen so many conflicting opinions on whether X4 PCIE effects performance...

The only games I would really need a second 6850 for would be BF3, Red Orchestra 2, and maybe Skyrim on ultra settings. I am seriously considering adding the second 6850 on the X4 slot and benchmarking before and after. That way I can put this debate to rest...

If worse comes to worse ill have an excuse to upgrade to an AM3+ mobo with two X16 slots


EDIT: Also, I am using a 32" Sony LED 1080P TV, which can be a bit taxing on a single 6850 even in BC2.


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## MonsterMiata (Jan 5, 2010)

KBeasley said:


> Thanks for all the quick responses. I consider myself pretty decent when it comes to hardware knowledge, however I have seen so many conflicting opinions on whether X4 PCIE effects performance...
> 
> The only games I would really need a second 6850 for would be BF3, Red Orchestra 2, and maybe Skyrim on ultra settings. I am seriously considering adding the second 6850 on the X4 slot and benchmarking before and after. That way I can put this debate to rest...
> 
> ...


Gcavan is correct about the x4 slot not being an issue. A quick google search proves him very much correct.


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## SpamHammer (Sep 21, 2011)

MonsterMiata said:


> You would be better off buying a better gpu like a 6950 or 6970 then swapping mobo's just to x-fire two slower cards that may improve performance. That x4 slot, while can be used for x-fire, will not provide any gains what so ever.
> 
> X-fire is not supported by all games and will most of the time cause more headaches then gains. Its a technology that needs a bit more time to mature before its really feasible as its simply not cost effective for the gains you receive.


"That is INCORRECT" buddy. You're spouting antiquated, outdated information that's been incorrect since at least the 5x00 ATIs, and to a lesser extent the 4x00 ATI cards.

AnandTech - Bench - GPU11

As you can see, two 6850s cleanly smoke a single 6950 by a good margin. 

Secondly, in nearly all modern games, Crossfire has a near- 100% scalability. 

Here you can see a single 6850 running 48 FPS in their test rig on Bad Company 2. The same card Crossfire'd runs at 94FPS. That's a 97.9% efficiency, and there are many games (I saw a thread on the efficiency tests of Crossfire vs. SLI somewhere, and I'll have to track it down later) where the efficiency is upwards of 98% to 99%. One even had a 100% efficiency. 
AnandTech - AMD

In truth, your comment about the lack of efficiency in games using crossfire WAS true- several years ago. Nearly all games these days, coupled w/ AMD's much improved drivers, run very efficient, bringing us the true promise of multi-GPU setups as we expected back when the technology debuted. 

Specifically for Battlefield BC 2 and Battlefield 3, these games are optimized for multiple processing streams to take advantage of two- and-four core processors, and multiple GPUs. The evidence is right there in that link I posted. 

I expect the Beta might not show a ton of performance improvement, but after launch as DICE updates the game for that, and NVidia and AMD update drivers, we'll see the performance nearly double.


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## SpamHammer (Sep 21, 2011)

KBeasley said:


> Thanks for all the quick responses. I consider myself pretty decent when it comes to hardware knowledge, however I have seen so many conflicting opinions on whether X4 PCIE effects performance...
> 
> The only games I would really need a second 6850 for would be BF3, Red Orchestra 2, and maybe Skyrim on ultra settings. I am seriously considering adding the second 6850 on the X4 slot and benchmarking before and after. That way I can put this debate to rest...
> 
> ...


I run Bad Company 2 on max'd settings at 1080p on a single 6850 at 60FPS, and this link provides a single 6850 running at Maximum Quality at 48FPS.
I'm curious what your PC setup is that 1080p would be taxing your 6850? You're probably CPU limited if you're being "taxed" at 1080p. 

Could you provide your specs?


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## SpamHammer (Sep 21, 2011)

KBeasley said:


> I have a Gigabyte 880-GA-UD3H Motherboard. It only has one X16 slot and one X4 slot. I currently have a Gigabyte Radeon HD 6850 and I'm looking to crossfire in time for Battlefield 3.
> 
> Would I be better off buying another 6850 and doing crossfire with the X4 slot? Or buying a new motherboard with two X16 slots?



I'm in the exact same boat as you! I'm going to go reserve Battlefield 3 today and I've been wondering the same thing. Just found out my damn mobo has a 16x and a couple of 4x slots.

Right now, I run Bad Company 2 at 1080p on my 24" 1080p LCD (so, no reason to crank the resolution up higher), at Maximum Quality settings and 8x MSAA, and I get 60 FPS consistently, according to FRAPS. Sometimes drops to 54FPS, but never below that. 

I get ~35-40 FPS on Crysis Warhead at the 4X AA, same settings. 

I'm trying to figure out whether or not to get another 6850 or 6870 (6870s are running $120-$150 on eBay from reputable sellers with perfect feedback- even lower than 6850s in the stores!) on my current mobo. 

Based on Gcavan's post, I'm thinking I'll get the beta the two days early, figure out where my baseline FPS and quality stand, then order one and drop it in.


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## MonsterMiata (Jan 5, 2010)

SpamHammer said:


> I'm in the exact same boat as you! I'm going to go reserve Battlefield 3 today and I've been wondering the same thing. Just found out my damn mobo has a 16x and a couple of 4x slots.
> 
> Right now, I run Bad Company 2 at 1080p on my 24" 1080p LCD (so, no reason to crank the resolution up higher), at Maximum Quality settings and 8x MSAA, and I get 60 FPS consistently, according to FRAPS. Sometimes drops to 54FPS, but never below that.
> 
> ...


I would not use a beta version of the game for a baseline. Card manufactures will not release optimized updates till after the game is released.

I would personally wait to see what your card does alone. You might be surprised.


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## SpamHammer (Sep 21, 2011)

*Edit* KBeasley,I see you listed a Phenom II X4 B55 on your profile. Is this still correct? 
IF so, your issue is that you're extremely CPU bottlenecked. Buying a second 6850 would be a waste vs. upgrading to a modern CPU.
Here is your CPU: PassMark CPU Lookup

As you can see, it scores 3833 points. My Core i5 2500k before overclock to 4.5GHz scores 7373. That's a 96% increase in performance. Clearly, if you're still running that slower CPU, that's the problem you're having, and I think you're going to run into issues on Battlefield 3. I would recommend upgrading the CPU before dumping more money into another bottlenecked GPU. No sense in handicapping a second one for that kind of money. 

These figures are of course assuming you've got all four cores unlocked, and are not simply running two cores on the Phenom II X2 555 that most people are running. 

You'll likely be able to play fine at lower resolutions like 1280x960 due to the CPU bottle necking your system. I didn't notice any perceptible difference on my machine in BC2 between the same settings at 1680x1050 vs 1920x1080.


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## SpamHammer (Sep 21, 2011)

MonsterMiata said:


> I would not use a beta version of the game for a baseline. Card manufactures will not release optimized updates till after the game is released.
> 
> I would personally wait to see what your card does alone. You might be surprised.


I would expect the Beta to be within 80-85% performance of the finished product. Considering the beta is launching 3 weeks before the game ships, I find it very unlikely that they've got the time to do any major optimizations, and besides, DICE wouldn't be showing a beta if they weren't comfortable with people judging it based on graphics, performance, etc.

But yes, you are correct, I will be running, for the first two nights at least, 1x 6850 to see what that does, and then make a decision.


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## Wrench97 (May 10, 2008)

Keep the thread on subject.


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## KBeasley (Dec 8, 2010)

@SpamHammer - My X4 B55 is overclocked to 3.82 GHz as well. Currently rates between 4800-5100 on the passmark charts. I do not think it is a bottleneck, but I have not ruled out a bulldozer upgrade since my motherboard will accept AM3+ chips. 

System Specs ---
Gigabyte 880GA-UD3H (SATA 3.0 & USB 3.0)
8 GB G.Skill DDR3 1333
AMD Phenom II X4 B55 @ 3.82 GHz
Gigabyte Radeon HD6850 (930 MHz Clock Speed, 1150 MHz Memory)
2 x 500 GB Seagate 7200 RPM
1 x 1TB Seagate 7200 RPM
Corsair TX650 PSU 


I with everything max, and 8x Anti Aliasing with "edge detect". This bumps it up to like 24x Anti Aliasing. With that enabled I get like 45-55 average. With 4x Anti Aliasing I get 60fps easy. 

I am going to wait and see on BF3. Hopefully my single 6850 will produce ~45-50fps... especially since BF3 is being developed for PC, is native DX11, and will make efficient use of multi-core CPU's. If all else fails, I now know that I can crossfire on a x4 slot. Thank you once again Tech Support Forum.


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## SpamHammer (Sep 21, 2011)

@KBeasely

Hey, I didn't know *45-55FPS* _w/_ 8XAA and Edge Detect was considered _"taxing"_. 
Guess we had a difference of definitions there.

I still think I'd upgrade the CPU first, but yes, a second GPU would help if your PassMark score is higher than the stock B55's in the range you were talking about. 
The stock B55 (w/ 4 cores enabled) scores lower than my brother's Core i3 2100, and I wouldn't dare waste time and money Crossfiring his without a CPU bump. 

Based on the FPS you're getting right now, I'm sure you'll be fine on Battlefield 3. I'll be watching this board. When you get the beta next week, post up your FPS and your detail settings, and a link w/ a screenshot of FRAPs running the FPS counter.

I'll do the same. Then we'll have something close to an apples-to-apples comparison across different chipsets.

I hear you on running it on a single 6850 first.
Still, there are several 6850s on ebay below $100 right now, with about a day left on them, no reserve, and I think those deals are too good to pass up. I'll likely get another one soon. :grin:


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## KBeasley (Dec 8, 2010)

BF3 Beta update:

With everything on Ultra (4x AA) I am only getting 18-25 fps outside and ~30 inside the subway :sigh:

On high I get a playable 30 fps average.


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## SpamHammer (Sep 21, 2011)

KBeasley said:


> BF3 Beta update:
> 
> With everything on Ultra (4x AA) I am only getting 18-25 fps outside and ~30 inside the subway :sigh:
> 
> On high I get a playable 30 fps average.


That's odd, according to many sites, almost all of them authority sites, the Beta has no difference between Ultra and High. They've theorized that when it ships, the big differences will be the AA and enabling tessellation.
The 6850s should be interesting, because the 6x00 series of cards was supposed to feature improved tessellation over the 5x00 series. 

Right now I am getting mixed results- it's not steady. One game session it will run 38-48FPS for me, everything max'd, including AA and HBAF, in the park. In the tunnel it's a more consistent 45-50FPS.

The next game session, it will run 29-37FPS in the park, 35-43 or so in the tunnels. I'm not sure why.

The one time I got into Caspian border it ran smoothly, except for the massive server lag that was widely reported.

I've got mixed feelings right now. Rush was never my thing in Bad Company 2 (though it was fun in BC1), but it feels real bad here. Give me classic Conquest! On top of that, all of the bugs, and the Battlelog interface, the lack of button mapping on the mouse, the squad issue (that should be fixed in the retail), etc. kind of has me burnt out on the beta. I stopped playing last night to play more BC2.

I do, however, love the NVIR scope. I racked up soooo many kills playing offense in the park, and even better, defense in the tunnels. 
Equip the SMG of either side w/ a bipod, IRNV scope, and silencer, and then spray short bursts to wipe out the opposition.
:grin:


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## Tyree (May 10, 2009)

Have either of you tried using one GPU to see the performance differences you are getting with two GPUs?


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## KBeasley (Dec 8, 2010)

I dunno about your theory, but when I use the auto setting (which puts everything on high, no AA) I can get playable frames 30+ outside and 50+ inside. 

I do agree, the rush mode feels too run and gun for me. This map is such a teaser for the rest of the game. I can't wait for big conquest maps! Especially urban maps with lots of destruction. Overall the gameplay feels very smooth though. It is definitely different from every other BF game that I have played, but I kind of like the new direction. 

The attachments are so awesome too. I absolutely love using the bipod on the LMG's. It is so fun to just mow people down inside the subway. Overall, I give the beta an 8/10 - only because its limited to rush, and Operation Metro is not the best map. Once the glitches are worked out and the full game releases, I can see myself playing this game for years to come!


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## SpamHammer (Sep 21, 2011)

Tyree said:


> Have either of you tried using one GPU to see the performance differences you are getting with two GPUs?


These are both single 6850 GPUs. Neither of our setups are dual GPU at the moment. We both came to the thread looking for info on whether or not it would be prudent to buy a second one. I will be getting a second one regardless, but I played again last night and was getting a solid 42+ FPS maxed at 1080P in the park, so I'm sure when the game launches, it will run even better.


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## Tyree (May 10, 2009)

Two GPU's rarely give any significant performance increase. Two GPU's do consume more power, generate more unneeded heat into the case for that small gain you get in the few games that can utilize two GPU's.
One better GPU is almost always the better option to improve graphics.


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## MPR (Aug 28, 2010)

Tyree is right about heat generation. Think of it this way -- under load, a modern high-end graphics card uses the same energy as two (or sometimes three) 100 W incandescent bulbs. Putting another graphics card into your computer case is like putting two 100 W bulbs in there. My little sister had an "Easy Bake" oven that used a single 100 W bulb to cook cakes and pastries.

That said, with the Radeon 6850 you actually may see substantial improvement in Crossfire _with some applications_. Reviewers found that two 6850's in Crossfire performed equivalent to one Radeon 5970 or a GTX 480 in synthetic benchmarks. However, in actual games this was often far less (with a couple of games Crossfire actually _dropped _framerates at certain resolutions). Several also noted the heat issue and said that it was nearly, but not quite, enough to recommend not using the 6850s in Crossfire (interestingly, 6870s ran cooler).

Your gaming rig is not going to be quiet if you do Crossfire -- you will need at least three fans at full speed to remove the heat from the case.

The 6850 is still a top-ten card and quite capable of running most games on high (though maybe not the highest) settings. However, in a couple of years when new games require something like a 480 for halfway decent frame-rates and the 6850 is priced $75 or less it might be worthwhile thinking about buying another one for a Crossfire setup.


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## KBeasley (Dec 8, 2010)

I am using the Rosewill Destroyer mid tower case. I currently have one front 120mm blowing directly on my hard drives and into the case. I have a rear exhaust 120mm, and two top 120mm fans as well. My CPU is cooled by a 92mm Xigmatec Rifle cooler. And my 6850 is a Gigabyte with their dual fan windforce cooler. The video card is honestly the quietest fan(s) in my case, and it never gets above 70c AND its overclocked. I love this card lol


That being said, as a rule of thumb you are very correct. Small case + two video cards = more heat. 

I do not think I am going to crossfire at the moment though. Maybe if I get a nice side job to pay for it - but right now my 6850 is performing quite well on high. And as was mentioned earlier, It will most likely run even better when the full release comes out and more driver tweaks are released. I did learn that if I need to in the future I can always throw another card in on my x4 slot and I will not get a performance hit. So, once again, I thank you TSF for you help!


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## SpamHammer (Sep 21, 2011)

Tyree said:


> Two GPU's rarely give any significant performance increase. Two GPU's do consume more power, generate more unneeded heat into the case for that small gain you get in the few games that can utilize two GPU's.
> One better GPU is almost always the better option to improve graphics.


You sir are _very_ incorrect in regards to performance increases with dual GPU setups. I've already covered that in depth in this very thread, as have 2 other posters.

More power consumption and heat generation is a given, seeing as there are _two_ of them, but I'm certainly not concerned with my electric bill when gaming. However, that is a great consideration when buying a second card: double check your PSU. 
I think that those are small considerations given the significant gains provided by two cards vs. one. In many cases, specifically the 6850s, it's been more cost effective and more performance-effective (if I'm being clear) to get two cards vs. 1. The dual 6850s out perform the top-end 6970, while being cheaper. I could get two 6850s new for around $300, but the 6970 was in the $400s, dipping into the upper $300s. Savings of $70-100. 
Performance chart is here: AnandTech - Bench - GPU11

Now, of course, at the end of the year w/ the 7000 series launch around the corner, and AMD's dual-chip GPUs out, the prices for the 6970 have been reduced, but you can still get two 6850s for the same price or less, and the performance is still better.:grin:


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## SpamHammer (Sep 21, 2011)

KBeasley said:


> I do not think I am going to crossfire at the moment though. Maybe if I get a nice side job to pay for it - but right now my 6850 is performing quite well on high. And as was mentioned earlier, It will most likely run even better when the full release comes out and more driver tweaks are released. I did learn that if I need to in the future I can always throw another card in on my x4 slot and I will not get a performance hit. So, once again, I thank you TSF for you help!


I think this was a great summary for this thread. I came here for the same reason, and after a lot of discussion (sometimes of greatly differing opinions), I've come away with the information needed. Thanks all for the help.


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