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Fx-8350 bottlenecking 2 x R9 280x?

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  • GPUs
  • Bottleneck
  • CPUs
Last response: in CPUs
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September 15, 2014 12:57:38 PM

Hey everyone, i just recently put together a gamin pc, with an AMD FX-8350 CPU and 2 x R9 280x running crossfire. Both CPU and GPU are running stock speeds, so no overclocking has been done, but the problem is that when ever i play battlefield 4 i average about 65-70fps with one R9 280x, but when i turn on crossfire and run 2 x R9 280x it almost seems if the fps drops and averages about 50-60 fps, im deffintly not seeing any improvements, can anyone please help me.

More about : 8350 bottlenecking 280x

a b à CPUs
September 15, 2014 1:05:42 PM

Yeah, the FX-8350 bottlenecks a single R9 280x, even more 2x of them, OC it as much as you can, that's all you can do without changing to an Intel platform.
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September 15, 2014 1:09:47 PM

yeah i really would like to upgrade to intel, but its gonna cost, so i guess i could start of with overclocking my current cpu and see how much it gives, thanks for the reply :) 
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a c 96 à CPUs
September 15, 2014 1:10:04 PM

That cpu doesn't bottleneck anything... If u were getting 65 fps why did ubl add another thought you can try ocing the processor to confirm... What power supply u running? Could be a voltage issue or perhaps a driver issue when using 2 certainly make sure all GPU/chip set drivers are updated
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a c 78 à CPUs
September 15, 2014 1:10:35 PM

yeah it's just that it doesn't bottleneck 1 card, but will bottleneck 2, oc the cpu to lessen the bottleneck, and maybe your board is running at a x16 x4 crossfire config
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September 15, 2014 1:12:17 PM

im running a 700w cooler master psu, and 14.4 amd catalyst center
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a c 149 à CPUs
September 16, 2014 7:33:51 AM

Adding an additional GPU, and thus possibly having a bottleneck for the potential of those two GPUs, would not hurt performance like what you are perceiving. It would limit the performance you would be able to achieve - so your performance would stay the same if you were already bottlenecked. If you were not bottlenecked, you would witness an amount of diminishing returns when you adding another GPU.

Here is some food for thought: http://www.overclock.net/t/1235557/official-top-30-heav...
Note the person using the FX-8350 near the bottom of the list, getting *merely* ~150 FPS with a Quad-crossfire 7970 rig. If you look up the list, you'll see another person with a Quad-crossfire 7970 rig, who got 40 FPS more (~190), but is using an I7-3930.

So, yes, the Intel has lessened the bottleneck, by an amount that isn't to be sneezed at. But, uh, the I7-3930 is also a six-core $600 piece of equipment. This is also a Quadfire set-up of GPUs. So, oh darn, the FX-8350 bottlenecks four fast GPUs, and makes it it to the bottom of a list of a recorded list of Top 30 benchmarking results. Clearly, it is an inferior CPU.

TL;DR - post your full computer specifications. Perhaps there is another bottleneck in your system that we can discover that is actually hurting your performance. You already mentioned your PSU - do you mind giving us more specifics about it? It could be that one of your cards is not getting enough power.
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September 16, 2014 10:41:13 AM

my specs are:

CPU: AMD FX-8350 Black - AM3+

MOBO: ASUS M5A99FX PRO R2.0

GPU: Sapphire Radeon R9 280x Running crossfire

SSD: samsung 840 120gb

HDD: Seagate Desktop SSHD - 1TB

RAM: Kingston HyperX Beast DDR3-1866 DC 8GB

PSU: Cooler Master B700 - 700W PSU
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a c 149 à CPUs
September 16, 2014 11:55:21 AM

That's actually a really nice rig, and, at first glance, it does look to me that the PSU may be inadequate - but I'll have to take a closer look after work to be sure.

AMD Overdrive should allow you to view the frequencies of the GPUs when you put it under a load - see what the frequencies are displaying. (Alternatively, maybe it's a thermal issue? They may be downclocking because of excessive heat, not lack of power.)

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September 16, 2014 12:13:23 PM

yeah im starting to realise that there's a hole lot of things that could be wrong, but im just gonna start from an end and see what will help, as it is right now im 85% sure im gonna switch to intel cpu (Intel Core i7-4820K Ivy Bridge-E) and new motherboard (GIGABYTE GA-X79-UD3) and incase that doesnt help, then i will most likely try another power supply. At first was just gonna try overclocking my current amd cpu, but i dont want something that will only just run it, and i really cant see any impressive future for amd at the moment. thanks for all the help so far, it's really appriciated :) 
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September 17, 2014 8:16:54 PM

Here's my setup, its similar to yours:
AMD FX 8350
Asus M5A 99FX PRO R2.0
16GB G Skill 1866
Samsung 840 250GB
2x Asus R9 280x in crossfire
Corsair H80i
Cooler Master V1000 PSU
Cooler Master HAF X

I have had absolutely no problems when running a single card, however, I have had mad frame drops and stuttering when using crossfire in multiplayer since installing Dragon's Teeth. If I'm playing on a map like Metro with only a few players I get between 150-200 fps on ultra preset at 1080p depending on where I am and what I'm looking at. If the server starts to reach 30+ players, my FPS drop severely to as low as 30-50 then spikes back into the 80's. Also note, all eight of my cores run like crazy even with Mantle and my memory usage has reached almost 12GB in game!!! I have tried other games like Tomb Raider and had no problems with crossfire. I think that between BF4 being such a demanding game and all the problems Dice has had with its optimizations you should probably not be so quick to blame your CPU. I've been losing my mind trying to diagnose my frame drop issue but everything keeps pointing to a possible bottleneck, or just this damn game. In your case, you should at least be getting much higher FPS on the test range. Also, you are running the recommended minimum PSU for only one card. I would highly recommend more for your crossfire setup, you may be starving them. That"s why I bought the V1000.
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