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Crossfire question - asrock extreme3 970

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September 3, 2012 11:57:46 AM

Hey so I built my computer about a year back, and I am looking to buy another 6850 to crossfire with my current one. The only problem I can see with this is that my motherboard has 1 16x pci and 1 4x pci slot. I am wondering if my motherboard will do what ivy bridge does (when xfired, both slots turn to 8x) automatically, or if I would need to tweak something in the bios.
Any help would be appreciated!
Thanks
a c 717 V Motherboard
September 3, 2012 12:37:24 PM

Well yeah, sure if you go from AMD to Intel Ivy Bridge the performance will go up. The difference in 1920x1080 on average you'll loose ~4% from PCIe 2.0 x4 vs PCIe 2.0 x16 on your system.

Your MOBO is x16/x4 so no it won't x8/x8. This article seems appropriate -> http://www.techpowerup.com/reviews/AMD/HD_5870_PCI-Expr...
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September 3, 2012 1:31:42 PM

jaquith said:
Well yeah, sure if you go from AMD to Intel Ivy Bridge the performance will go up. The difference in 1920x1080 on average you'll loose ~4% from PCIe 2.0 x4 vs PCIe 2.0 x16 on your system.

Your MOBO is x16/x4 so no it won't x8/x8. This article seems appropriate -> http://www.techpowerup.com/reviews/AMD/HD_5870_PCI-Expr...


Ok thanks! So basically if i want to crossfire 6850's, I would need to get a new motherboard? I could also just save more money and replace the one 6850 with a single 7xxx series card, if it would be more straight foward.
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a c 717 V Motherboard
September 3, 2012 1:48:13 PM

No, you can use your current MOBO and CF x16/x4 and look at the scaling link I provided.

As far as the HD 6850 in CF vs a single HD 7000 series it depends on which AMD GPU and the games you are running or plan to run. As long as you can keep 45 minimum FPS then there's no need to replace/add a GPU.

I strongly recommend that you look-up benchmarks on your platform before purchasing anything.
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September 3, 2012 2:14:32 PM

jaquith said:
No, you can use your current MOBO and CF x16/x4 and look at the scaling link I provided.

As far as the HD 6850 in CF vs a single HD 7000 series it depends on which AMD GPU and the games you are running or plan to run. As long as you can keep 45 minimum FPS then there's no need to replace/add a GPU.

I strongly recommend that you look-up benchmarks on your platform before purchasing anything.


Ok i checked the site again and it looks like i'll only lose 5-6% performance in 4x mode as opposed to 16x. Does that sound right? i did some benchmarking on bfbc2 on medium - high settings and got an average of 38 fps but dropped to 19 - 26 during explosions / thick foliage. I did a benchmark on gta4 with low - mid settings and I would get 15 fps when explosions and 20 in heavy traffic. I am also thinking about oc'ing my cpu to increase the performance in these games because lagging everytime an explosion happens in an fps is a slight problem.
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September 3, 2012 2:32:54 PM

I have the same board and run 2 6850's in x-fire just fine..Runs great..i suggest drivers 11.4 for 6850's avoid the newer stuff you lose performance..And don't forget to install CAP..
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a b V Motherboard
September 3, 2012 2:41:43 PM

Well, If you are going to get another HD6850 very cheap, it is worth the crossfire. But if you are planing to get it new... at its full price, lets say $150, you better save for a 210 HD7850, which is a decent upgrade.

Crossfiring x16 + x4 instead of x16 + x8 or x8 +8 is almost null in mid range cards. It comes in play with High end cards that needs the full bandwidth to use its full potential.

I crossfired my HD6790 in my motherboard (same as yours) and It was pretty good in battlefield 3 multiplayer. I really liked it, and if i am able to hand that card for cheap i surely i will be getting it.
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a c 717 V Motherboard
September 3, 2012 4:07:15 PM

bobochez said:
Ok i checked the site again and it looks like i'll only lose 5-6% performance in 4x mode as opposed to 16x. Does that sound right? i did some benchmarking on bfbc2 on medium - high settings and got an average of 38 fps but dropped to 19 - 26 during explosions / thick foliage. I did a benchmark on gta4 with low - mid settings and I would get 15 fps when explosions and 20 in heavy traffic. I am also thinking about oc'ing my cpu to increase the performance in these games because lagging everytime an explosion happens in an fps is a slight problem.

The differences vary, the ~4%, is an average. The cheapest 'fix' is to CF your current HD 6850, but you need to read below first.

Keep in mind a couple things both the CPU and GPU(s) have inherent limitations, plus CF/SLI scaling varies from game to game. The HD 6850 problem in some games, in particular many newer games w/higher settings, is 1GB of vRAM (vRAM Bottlenecking) and using applications like FRAPS (real time) or GPU-z (~1 sec polls/newer versions) will provide a lot of additional information.

Meaning if your problem really is maxing-out your vRAM or in some games reducing your Shared Memory (optimal) to the GPU (no Free) memory either or both can stop you in your tracks before the 'rendering' is really a factor. Because of this 'now' I recommend 2GB GPU(s) with 8GB RAM as minimums.

The games you mentioned 4GB minimum of Physical memory and with lower settings 1GB of vRAM should be enough. I'd also try to disable vSync. nVidia to a degree with Adaptive vSync has fixed some of the problems when vSync is Enabled, in some cases it can really drop the frames (explosions/lot of rendering/details/etc) -- the downside is 'tearing'. However, it's worth exploring.
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September 4, 2012 4:51:42 AM

jaquith said:
The differences vary, the ~4%, is an average. The cheapest 'fix' is to CF your current HD 6850, but you need to read below first.

Keep in mind a couple things both the CPU and GPU(s) have inherent limitations, plus CF/SLI scaling varies from game to game. The HD 6850 problem in some games, in particular many newer games w/higher settings, is 1GB of vRAM (vRAM Bottlenecking) and using applications like FRAPS (real time) or GPU-z (~1 sec polls/newer versions) will provide a lot of additional information.

Meaning if your problem really is maxing-out your vRAM or in some games reducing your Shared Memory (optimal) to the GPU (no Free) memory either or both can stop you in your tracks before the 'rendering' is really a factor. Because of this 'now' I recommend 2GB GPU(s) with 8GB RAM as minimums.

The games you mentioned 4GB minimum of Physical memory and with lower settings 1GB of vRAM should be enough. I'd also try to disable vSync. nVidia to a degree with Adaptive vSync has fixed some of the problems when vSync is Enabled, in some cases it can really drop the frames (explosions/lot of rendering/details/etc) -- the downside is 'tearing'. However, it's worth exploring.


Wow , thank you for all this inffo! I really appreciate it :)  I have 8gb of 1600mhz ram currently. Is what you are saying that the problem may be coming from not having enough vram? I do not use fraps or gpu-z (fraps makes me lag horribly and i'v never seen gpu-z before) but should i try running. Bfbc2 with fraps running to record what my computer is utilizing to run the game? Sorry if these are dumb questions, im a bit confused.
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a c 717 V Motherboard
September 4, 2012 1:32:05 PM

Either application shows Frame Rates and vRAM Usage. Regard FRAPS, I'm not suggesting you use it for 'capture' purposes and instead vRAM monitoring, but if it's causing a problem then use GPU-z. GPU-z will show a chart after the fact so simply run it in the background (see below).

I've linked both applications above.

Example GPU-z:
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September 6, 2012 4:45:12 AM

horaciopz said:
Well, If you are going to get another HD6850 very cheap, it is worth the crossfire. But if you are planing to get it new... at its full price, lets say $150, you better save for a 210 HD7850, which is a decent upgrade.

Crossfiring x16 + x4 instead of x16 + x8 or x8 +8 is almost null in mid range cards. It comes in play with High end cards that needs the full bandwidth to use its full potential.

I crossfired my HD6790 in my motherboard (same as yours) and It was pretty good in battlefield 3 multiplayer. I really liked it, and if i am able to hand that card for cheap i surely i will be getting it.


Ok cool, I think im probably just going to get a 6850 and xfire caus from what i can tell, basically there isn't really a problem unless i am ocd about benchmarks (I just wanna play games at nice frame rates :D  )
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September 6, 2012 4:46:17 AM

T-Frost said:
I have the same board and run 2 6850's in x-fire just fine..Runs great..i suggest drivers 11.4 for 6850's avoid the newer stuff you lose performance..And don't forget to install CAP..


Whats Cap?
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September 6, 2012 4:50:02 AM

jaquith said:
Either application shows Frame Rates and vRAM Usage. Regard FRAPS, I'm not suggesting you use it for 'capture' purposes and instead vRAM monitoring, but if it's causing a problem then use GPU-z. GPU-z will show a chart after the fact so simply run it in the background (see below).

I've linked both applications above.

Example GPU-z:
http://i.imgur.com/xSO21.png



Ok im getting a bit confused with all the technical details, so would getting another 6850 give me the extra 1gb of vram that i may or may not need depending on the gpu-z info?
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a c 717 V Motherboard
September 6, 2012 1:17:04 PM

Again, run 'GPU-z' or 'FRAPS (on screen)' and look at your vRAM usage, and if the vRAM is constantly being filled then you might want to consider a different GPU <or> if the vRAM is not being maxed-out then get a second GPU.
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September 6, 2012 1:37:25 PM

jaquith said:
Again, run 'GPU-z' or 'FRAPS (on screen)' and look at your vRAM usage, and if the vRAM is constantly being filled then you might want to consider a different GPU <or> if the vRAM is not being maxed-out then get a second GPU.


Ohhhh i see. So i will go do a test and see what gpuz says and then if the vram is being filled then i should get a single 2gb gpu as opposed to crossfiring?
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a c 717 V Motherboard
September 6, 2012 2:10:44 PM

Yep. There's plenty of games (now) that use 1.5GB~1.8GB+ vRAM on 1920x1080, but if they're not the games you play then it irrelevant.

Again, an example of a vRAM bottleneck is as you described e.g. explosions or out of the ordinary 'activity' where the rendering can drop to single digits for periods of time, and no matter how 'fast' your GPU is it can be bottlenecked to its' knees -- the cure is a new GPU with more vRAM.
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a c 717 V Motherboard
September 6, 2012 2:20:24 PM

Otherwise IF you have vRAM Bottleneck issues and can live with the occasional 1~9 FPS but want the other 98% of the time increased frame rates then CF your current GPU.
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September 6, 2012 2:47:07 PM

jaquith said:
Otherwise IF you have vRAM Bottleneck issues and can live with the occasional 1~9 FPS but want the other 98% of the time increased frame rates then CF your current GPU.


Awesome thanks! I will be at my computer on friday so ill test it then :D 
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September 7, 2012 6:31:53 PM

CAP = Crossfire Application Profiles.. Tells the drivers how to run x-fire for different games for max performance and compatibility..The download is on the same page as the drivers just further down the screen..I found it helped to run it even when i had 1 card..Really helped in BF3 ,stopped my cpu spikes..Worked for my friend running a 5770 too..installed cap and cpu spike gone..No idea why..lol
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September 14, 2012 12:15:41 AM

T-Frost said:
CAP = Crossfire Application Profiles.. Tells the drivers how to run x-fire for different games for max performance and compatibility..The download is on the same page as the drivers just further down the screen..I found it helped to run it even when i had 1 card..Really helped in BF3 ,stopped my cpu spikes..Worked for my friend running a 5770 too..installed cap and cpu spike gone..No idea why..lol


Ok thanks, i will install it.
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