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Crossfire urgent help requested

So im really confused about this fuss pcie 3.0 x16 and pcie 2.0 x4 i basically have this build on my pc:

LED ACER 27" G276HLA FULL HD --- 810 DHS
Intel CPU i5 - 4670K 3.4 Ghz 6MB Cache
Asrock Motherboard Z97 Killer
Circle Casing Fan x 3
Razer Mouse pad speed medium
Seidon 120V Liquid cpu cooler
HCG PSU Antec 620W
Coolermaster K350 case
Razer Mouse naga hex wraith edition mmo
BALLISTIX Crucial ram ddr3 1866 4gb x2
TRUST GXT 340 7.1 Headset
Coolermaster Sickleflow casing fan
LG DVD/RW
Transcend 340 SSD 128GB
HDD Seagate barracuda 500gb
ASUS DirectCU II V2 R9-280X 3GB GDDR5

and i have an extra r9 280x v2 laying around in my house somewhere as i got 2 r9 280x for 300$ now im wondering if i put the 2nd card will i suffer from alot of fps loss or ill get boost or anything please im really so confused about this i cant find a good chart for r9 280x crossfire on pcie 3.0 x16 and pcie 2.0 x4
11 answers Last reply Best Answer
More about crossfire urgent requested
  1. it may, may not. depends if the game is good at crossfire or not.

    You COULD plug it in, and try it all by yourself. You already have the cards, the board, plug them in, play a game. Better FPS? Then go with it. Worse FPS, take it out and sell it or buy a better board.

    And this is in no way URGENT.
  2. wait oops i forgot to say the thing is im afraid my psu wont handle it... although i checked on eXtreme vision psu calculator and it says my system will run at 599W at 100% load..
  3. Your motherboard has one PCI-E 3.0 16x interface and one PCI-E 2.0 16x interface. Either of those will provide more than enough bandwidth for your video card. You can definitely run both cards in crossfire in that motherboard.

    You power supply on the other hand is quite short for this task. It should be able to run it, but with both cards, but it will be under heavy stress. Not a long term solution.
  4. so you basically want to tell me i will just snap that thing on my motherboard and run it? ill downclock my cpu and unplug few fans ill replace my psu as possible in like few weeks is it safe to run it on my antec hcg 620?
  5. and it runs pcie 3.0 x 16 and pcie 2.0 x16 on x4 mode i guess
  6. Murissokah said:
    Your motherboard has one PCI-E 3.0 16x interface and one PCI-E 2.0 16x interface. Either of those will provide more than enough bandwidth for your video card. You can definitely run both cards in crossfire in that motherboard.

    You power supply on the other hand is quite short for this task. It should be able to run it, but with both cards, but it will be under heavy stress. Not a long term solution.


    But the 2.0 slots downgrades to 4x when used in crossfire, so crossfire gives 16x/4x. Which is the minimum AMD requires for crossfire labelling.
  7. is the 16x/4x is it like super bad i dont get it...its killing me..its not wroth to crossfire? or is it gunna be like it runs well on some games and wont run well on the other..?
  8. anyone ?
  9. It is not super bad. Typically, bus limitation will hold you back about 20% at most. Haven't seen what it will do to a 200 series cards, though, those are entirely reliant on the BUS since they have no crossfire bridge. I'd still try it anyway.

    About the power, yes you can snap it in and run it. Antec makes decent PSU's so it surely won't blow in your face or suddenly die on you. It will be operating quite close to the design limitation, though, so I'd seriously consider a new one if this becomes a permanent situation.
  10. Best answer
    I couldn't find any data on Crossfire 280X's under those settings, but since it is basically a 7970:



    This should give an idea of how much the bandwidth limitation actually impacts performance. In the above benchmarks there was a 7% difference between operating in PCI-E 3.0 x16 and PCI-E 2.0 x4. There might be a bit of amplification on that difference due to the lack of a bridge and the crossfire setup, but still hardly enough to make crossfire not worth it.
  11. I will run it and report back with some results cause the internet lack this kind of configuration
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