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Does my AMD FX 8150 CPU Bottleneck GPU HD 7990?

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January 18, 2014 3:48:21 PM


Hello all,
I was trying to build one of those High-end gaming pcs.
I run games like Arma 2, Arma 3, and for some reason I can't get the performance in high-ultra settings I was expecting from this machine.

FPS changes considerably when changing the in-game view distance.
I'm suspecting the cpu bottlenecks the GPU as I don't get more than 40% GPU usage in crossfirex (even though I'm certain it's on).

system:
AMD FX-8150 Eight Core Processor - 3.60GHz, 16MB, L3 Cache, Socket AM3+
Gigabyte SKT-AM3+ 990FXA-UD5 Motherboard (Rev 1.0)
Asus AMD Radeon HD 7990 Graphics Card (6GB, GDDR5, PCI Express 3.0)
Samsung 840 Series Pro 256GB 2.5 inch SATA Solid State Drive
Corsair DDR3 XMS3 8GB
OCZ OCZ-ZX1000W-UN 1000W
Zalman CNPS12X Heatsink and Fan

Cheers,
Nach1
a b à CPUs
January 18, 2014 3:53:44 PM

it shouldnt, your CPU is pretty high end as it is.
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January 18, 2014 4:04:25 PM

Thanks babachicken. When connected all for the very first time, I was expecting to have amazing fps... I can't figure out what could be the problem. All drivers are up to date and I have searched in every single internet forum.

My main concern is the reason why GPU usage is that low when playing. I did disable the ULPS but nothing changed
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a b à CPUs
January 18, 2014 4:05:44 PM

That CPU wouldnt bottleneck two titans let alone two 7970s. Its most likely xfire optimization and drivers, plus it takes a lot of vram and system memory to run high view distances on games like arma 3. Even the best of the systems will struggle with those games if you want to move every slider to the max and run every detail maxed out. You'll just have to find a compromise that works for you between view distance and terrain/object details.
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a b à CPUs
January 18, 2014 4:07:07 PM

it is strange, you have sufficient power supply, are there any CPU hungry processing running in the back?
is your CPU or GPU overheating causing it to throttle?
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January 18, 2014 4:19:34 PM

Thanks Maxiim for your reply. It gives me some hope in this machine after all.
Babachicken, CPU and GPU are always running smooth. I'm trying to find the way of getting both 7970 cards working at least 90% each to check performance and FPS.

Any thoughts about xfire configuration?
maybe something to do in bios?
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a b à CPUs
January 18, 2014 4:21:43 PM

baba is incorrect. that CPU COULD bottleneck a GPU in a lightly threaded game. And maxiim is just flat out wrong. The 7990 has 3GB per card which is plenty and increasing graphics and detail settings INCREASES the load on the GPU which means higher GPU usage and LESS of a CPU bottleneck.

obviously if you are at 40% there is a major problem. the one thing he said right was it may be a crossfire/driver issue. if you want to see if there is a CPU bottleneck you look at CPU usage.
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a b à CPUs
January 18, 2014 4:25:01 PM

wait, this may be a dumb question, but since the 7990 is a dual gpu... it need to be ran in xfire?
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January 18, 2014 4:28:52 PM

On AMD catalyst control center you have the option for that. It's on when I run those games
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January 18, 2014 4:42:03 PM

I just run Arma 3 with every single settings maxed out. FPS = 15

CPU usage 40%
GPU1 max usage 56
GPU2 max usage 36 (not used even)

It seems GPU2 only is switched on for a second... while the GPU1 is the one working out the game

I'm using 13.11b drivers for HD7990 (as with 13.12driver I had the same issue)
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January 18, 2014 4:50:24 PM

Now, when running Batman Arkham City GOTY, both GPUs worked synchronised (average 46% usage) but I felt some micro stuttering even though FPS do not go down a lot. I don't know what I do wrong. Do you guys think I'm missing some setting in bios? or is it vram affecting (it's the cheapest component on this pc)
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a b à CPUs
January 18, 2014 5:03:44 PM

The microstuttering is to be somewhat expected when running xfire or sli. I just fired up arma 3 ran, ran editor went to altis flew a chopper around for a bit on my setup @1440p my 780 didnt run above 40% no matter if everything is on ultra or high, so I'm quite positive its the game/engine itself in the arma series, try something like battlefield 4 if you have it, that game gets my GPU usage quite high. And unskol before you go claiming someone is "flat out wrong" play the game, mess with the settings a bit and see what you come up with.
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January 20, 2014 9:15:22 AM

maxiim said:
The microstuttering is to be somewhat expected when running xfire or sli. I just fired up arma 3 ran, ran editor went to altis flew a chopper around for a bit on my setup @1440p my 780 didnt run above 40% no matter if everything is on ultra or high, so I'm quite positive its the game/engine itself in the arma series, try something like battlefield 4 if you have it, that game gets my GPU usage quite high. And unskol before you go claiming someone is "flat out wrong" play the game, mess with the settings a bit and see what you come up with.


Thanks Maxiim.
I checked in battlefield 3 and Crysis 2 and fps =60. all running good.
I'll check what can I do with VRAM and see if I can make better experience in ARMA games.
regards,
Nach1

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January 21, 2014 6:00:26 AM

Hello again,
disabling paging file = my solution (sort of). I did not know by switching that off will increase sooo much the in-game performance. I can now set ARMA 3 view distance to around 4kms in all Ultra settings and feel I'm playing at 60fps (even though actual fps are 25 ???).

Once again, thank you all for your replies
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!