Topic Title: poor performance of crossfired 7870
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Created On: 08/18/2013 06:02 AM
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 08/18/2013 06:02 AM
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Grinding Levels

Posts: 170
Joined: 08/17/2013

hi everybody, 

i have a problem going on and i need expert advice.
2 months ago i purchased my best friend's pc, as he got a new one. 
this one had:

amd phenom x4 9950 2.6 ghz quad core black edition
4 gb ddr2 ram 800 mhz
asus m3a32mvp-deluxe
sapphire hd 4890
550 watt xfx psu
windows 7 64 bit

as i got his pc next to nothing, i started to upgrade his system for myself.

got a brand new gigabyte 7870 2gb and the fps i got on bf3 was around 40 to 60 fps on medium quality and native resolution of 1440x900.

i recently got another gigabyte 7870 2gb to do the crossfire, after some struggles finally i got it and installed it properly in my pc. 

booted the system, ran bf3, BAM! 20 to 40 fps!!!

researched the web, got CAPs for amd catalyst, no change in performance.

flashed the mobo bios to a new version, nothing.

added another 4gb ddr2 ram 800 mhz (now 8gb total) the system got slower!

disabled the crossfire, tested both gpus on their own pci-e slots and got 40-60 fps in bf3, ran the crossfire again and i got 20-40 fps....

what is wrong with my pc?




thanx everyone!

i updated my pc to amd fx 8350 with 8gb ddr3 and a 750 watt psu and i can get 60-to-150 fps easily.

thank you all! 


AMD FX8350//Corsair vengeance DDR3 CL9 8GB@1600//Asus ROG Crosshair V Formula z//Asus R9 290X oc DCII//Corsair CX750//Razer Lycosa//Corsair M30//Zalman Z11 plus case//Kingston 120gb SSD//Yamaha Audiogram6//Windows 8.1 64bit//

Edited: 08/24/2013 at 01:27 PM by deathcrush87
 08/18/2013 08:58 AM
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Posts: 26
Joined: 05/30/2013

Cpu bottleneck, check task manager in game, if your cpu is hitting 100% thats the issue.try overclocking your cpu.
I have 2 x 7870 and a 3570k @ 4.3 ghz and I still get bottlenecked in certain cpu intensive games (Bf3 multiplayer) 


2 x Asus Directcu2 7870,16gb Corsair vengeance,Gigabyte Z77X D3H,Intel 3570k @ 4.3 ghz,Corsair TX850m

Edited: 08/18/2013 at 09:45 AM by M0n0LiF
 08/18/2013 11:46 AM
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Master Looter

Posts: 312
Joined: 09/16/2012

First a 550W psu is NOT enough to power two 7870 cards you need at least a 750w to run them safely but I don't think this is your problem.

It looks to me like what MOnOLif said "cpu bottleneck" two 7870 are way too much for a first gen phenom with DDR2 ram to handle and even if you OC your 9950 your still going to bottleneck those 7870.

Just a pointer

When you start to upgrading your system ALWAYS check to see if your psu can handle the new hardware. If you put to much stress on it depending on its age it could fail and take your new hardware with it or it will start cousing other problems.


FX 8320// Asus Sabertooth R2.0 // HIS R9 280x //8Gb of 1866Mhz ram, H50 cooling, HX850W psu all stuffed into a NZXT Phantom case.

Was a member of AMD Processer forum since 2008. Last post count 1818.

 08/18/2013 06:33 PM
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80 Column Mind

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Joined: 04/17/2008

If you overclocked the 7870s they would be pulling close to 200w each and with the 9950 being either a 125 or 140w part itself, plus another 50w for the rest of your system, Slayerx is right that a 550w PSU is not sufficient, a 750w should be your target. And they are correct your CPU is to slow, the generation 1 and 1.5 Phenom's were quite underwhelming both in speed and IPC. You're best option would be to pull your drives and video cards and do a complete system update. $490 can get you the RAM, CPU, and Motherboard I have now, plus whatever you spend on a quality power supply which ranges from about $90 for a Corsair to $150 for a SeaSonic.

AMD FX-8350 w/ Corsair H105, ASUS Sabertooth 990FX Gen3/R2, 8GiB G.SKILL DDR3-2133, XFX HD 7970 GHz Edition, 1TB Samsung 850 Evo, 256GB OCZ Vector, Creative X-Fi Titanium w/ Creative Gigaworks S750, SeaSonic X750, Corsair C70, HP ZR2440w, Win 7 Ult Ed x64
 08/19/2013 11:21 AM
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Case Modder

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Joined: 01/05/2013

Yeah, motherboard and psu need updating...get DDR 3 memory (medium speed), too.




Non-noob components.

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