Crossfire Different PCIe

[wlaro]

Hello my mobo has 1 PCIe 3.0 x16 and 1 PCie 2.0 x16 supports up to x4

Can i crossfire 2 amd 7970 reference edition

[SWAGGA]

Hello my mobo has 1 PCIe 3.0 x16 and 1 PCie 2.0 x16 supports up to x4

Can i crossfire 2 amd 7970 reference edition

pcie 2.0 x4 is too slow, it would bottleneck

[X_Rated_Box]

Brand and Name of motherboard? But nevertheless i think that that should work (but you should consider upgrading your motherboard before you go sli when you dont even know if SLI is supported)

[wlaro]

pcie 2.0 x4 is too slow, it would bottleneck

but my mobo is b85 g43 gaming and in the site of msi it say enable crossfire

[thekeemo]

if the motherboard says its crossfire capable yes

[Glenwing]

pcie 2.0 x4 is too slow, it would bottleneck

Barely... It'd be a 10% loss at most.

There shouldn't be any technical problems getting crossfire to run AFAIK but I am not positive what happens when you run one card from the CPU/northbridge and one from the southbridge (which is what's going on here).

It's probably a good idea to just look for the CrossFire logo on the board, if it isn't present it may not work.

[Kyuubixchidori]

pcie 2.0 x4 is too slow, it would bottleneck

It bottlenecks like 3-5%. I ran 2 7970s overclocked and it was just fine at 2.0 x4. Higher end cards like 980s would bottleneck though

[wlaro]

so it should work?

i need 6gb fo GTA5

 

It bottlenecks like 3-5%. I ran 2 7970s overclocked and it was just fine at 2.0 x4. Higher end cards like 980s would bottleneck though

[Sakkura]

It bottlenecks like 3-5%. I ran 2 7970s overclocked and it was just fine at 2.0 x4. Higher end cards like 980s would bottleneck though

 

Wouldn't work on Nvidia anyway, since SLI requires 8 lanes per card. AMD is less picky and allows Crossfire with 4 lanes.

[Aphala]

I would think so - https://www.pugetsystems.com/labs/articles/Impact-of-PCI-E-Speed-on-Gaming-Performance-518/

[Sakkura]

so it should work?

i need 6gb fo GTA5

 

It would work, but performance might not be optimal.

 

You won't get 6GB effectively, since the memory does not add up. Two 3GB cards in Crossfire (or SLI) still gives you 3GB effective VRAM.

[wlaro]

Wouldn't work on Nvidia anyway, since SLI requires 8 lanes per card. AMD is less picky and allows Crossfire with 4 lanes.

But there's a big difference between a FPS crossfire x16 / x16 and one x4 / x4?

[Sakkura]

But there's a big difference between a FPS crossfire x16 / x16 and one x4 / x4?

 

This article suggest you'd lose around 6% performance. That's based on single cards though, and on older drivers.

[wlaro]

This article suggest you'd lose around 6% performance. That's based on single cards though, and on older drivers.

so I can not use the video card to 100%

[wlaro]

This article suggest you'd lose around 6% performance. That's based on single cards though, and on older drivers.

I want to know if i put 1 amd 7970 on pcie 3.0 x16 is the same of 2 amd 7970 pcie 3.0 X4 and PCie 2.0 x4?

[Sakkura]

so I can not use the video card to 100%

 

No, but you get like 94% out of it.

 

I want to know if i put 1 amd 7970 on pcie 3.0 x16 is the same of 2 amd 7970 pcie 3.0 X4 and PCie 2.0 x4?

 

Not sure what you mean here.

[ThatOneGuyThatOnlyPlaysPC]

pcie 2.0 x4 is too slow, it would bottleneck

I agree it's not worth it if the second slot is only x4

[wlaro]

.

[wlaro]

No, but you get like 94% out of it.

 

 

Not sure what you mean here.

But 7970 on pcie 3.0 x4 get 99% and PCie 2.0 x4 get 94 %

[Kyuubixchidori]

I agree it's not worth it if the second slot is only x4

it works just fine. 94% loss at 60 fps 4 frame drop. bf4 maxed out I could easily get into the 140-150fps range with 1080p Maxed out, without even turning mantle on. so no, it seems like it should be but it is not a bottleneck in any way

 

But there's a big difference between a FPS crossfire x16 / x16 and one x4 / x4?

nope. you will be fine. and my set up was even more janky, 7950 in one slot and a 7970 in the pcie 2.0 4x slot