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Crossfired 7970s slower than one alone?

Tags:
  • Crossfire
  • Gigabyte
  • Graphics
Last response: in Graphics & Displays
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November 18, 2013 11:38:50 AM

I've seen and read about this issue but have not seen a solution anywhere. I have two Gigabyte GV-R797OC-3GD cards (added #2 this week), linked in the following system:

Antec Full Tower/New Rosewill RBR1000-M 1000W PSU
Gigabyte GA-P67X-UD3-B3
Intel i7 Sandy Bridge at 3.8gz
8Gb Crucial
64 GB SSD/ 2TB 7200
2-Gigabyte GV-R797OC-3GD in Crossfire.

Both cards show up fine in GPU-Z and CCC, Crossfire mode enabled, nothing overclocked. One odd thing is the power meter in CCC Overdive, it shows 0 for Card #2 and all the Ghz clocks are at 0 also. Is that normal? In the three games I currently mess about with - BF3, ARMA2 , And ARMA3. Issue is the frame rates are no better, and at some points actually seem worse with Crossfire enabled! I bought the second card to increase FR and eye candy, not decrease it!

Thank you for any help..

More about : crossfired 7970s slower

November 19, 2013 6:32:54 AM

An update to what I have tried -

Flashed video cards to latest (F3) BIOS
Flashed motherboard to latest (F10b) Bios

Tested, still not great frame rates in ARMA3
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Best solution

November 19, 2013 6:42:23 AM

Arma just doesnt like multi gpu setups. ive had my CF setup for around 1.5yrs and nothing will stop them.
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November 19, 2013 6:45:15 AM

Thanks, guess i'll have to broaden my horizons and see how it does in other games!
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November 19, 2013 4:20:11 PM

I have exactly the same cards as you do (as you can see in my sig) and I have no issues with anything. Admittedly, I haven't tried Arma III although according to [H]ardOCP, twin HD 7970s work great in Arma III:

Use the latest beta drivers from ATi and you should be ok. They were designed to increase crossfire gains. If you're using the driver from the disc that came with the card(s), that could be your problem. It's normal to see the second card at 0 in Windows because Windows doesn't use more than one card. If you want to see card #2 in action, load ccc, watch the second card, and load something like Unigine Heaven or 3DMark. That will make that second GPU magically come to life. It's a power-saving feature. One card goes idle when it's not needed.
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November 19, 2013 6:15:46 PM

Avro Arrow said:
I have exactly the same cards as you do (as you can see in my sig) and I have no issues with anything. Admittedly, I haven't tried Arma III although according to [H]ardOCP, twin HD 7970s work great in Arma III:
Use the latest beta drivers from ATi and you should be ok. They were designed to increase crossfire gains. If you're using the driver from the disc that came with the card(s), that could be your problem. It's normal to see the second card at 0 in Windows because Windows doesn't use more than one card. If you want to see card #2 in action, load ccc, watch the second card, and load something like Unigine Heaven or 3DMark. That will make that second GPU magically come to life. It's a power-saving feature. One card goes idle when it's not needed.


Updated BIOS on both cards and got latest drivers. Ran BF3 and got between 125 and 200FPS on full Ultra settings. Ran a couple Benchmarks -

Unigine Heaven Benchmark 4.0
FPS: 124.4
Score: 3133
Min FPS: 30.3
Max FPS: 212.0
System Platform: Windows NT 6.2 (build 9200) 64bit
CPU model: Intel(R) Core(TM) i7-2600K CPU @ 3.40GHz (3409MHz) x4
GPU model: AMD Radeon HD 7900 Series 13.152.1.8000 (3072MB) x2
Settings
Render: Direct3D11
Mode: 1920x1080 4xAA fullscreen
Preset Custom Quality High
Tessellation: Disabled

Ran 3DMark,
Icestorm scored 135246
CloudGate scored 23248
Firestrike scored 11470 - "better than 96% of all results"

Seems like BF3 and Benchmarks are working great. I unchecked the tick box for using Crossfire in games with no profile but havent tried ARMAII and III yet to see how they work.. will try tomorrow.
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!