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Tom's Hardware > Forum > Graphics & Displays > AMD Radeon > [Solved] Radeon 7970: dual 16x vs. dual 8x

[Solved] Radeon 7970: dual 16x vs. dual 8x

Forum Graphics & Displays : AMD Radeon [Solved] Radeon 7970: dual 16x vs. dual 8x

Best answer from FunSurfer.

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As absurd and overkill as it is, I was wondering if there was a large difference in performance if you would run two Radeon 7970s in crossfire in 16x speeds versus 8x.

Thanks! :D

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A difference of ~10% between the 2 configurations I would say. The 7970 will fully saturate the x8/x8 slots in some cases - especially when overclocked.

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Reply to deadjon

7970 is a high end card, therefore it's most likely to have full bandwidth of 16x/16x to work %100 without bottleneck. If you want a board that has x8/x8 (PCI-E 2.0 mostly) I'd recommend you to get x16/x16 instead.

Reply to refillable

refillable wrote :

7970 is a high end card, therefore it's most likely to have full bandwidth of 16x/16x to work %100 without bottleneck. If you want a board that has x8/x8 (PCI-E 2.0 mostly) I'd recommend you to get x16/x16 instead.



Yeah but if as deadjon said the difference is only a minimal 10% I'd stick with the 8x speeds. For now anyway I'm going to use a single card which will run at 16x and that should be more than enough for the time being. If I want a dual 16x I would also need to get a x79 board which runs on the overpriced i7-3960 since the intel socket 1155 boards I'm looking at don't apparently support dual 16x speeds.

Btw the slots will be 3.0 dunno if that makes a large difference to a 8x speed 2.0 slot...


Message edited by tha1 on 02-10-2012 at 01:13:19 PM
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There is almost no bottleneck with 7970 on PCIe 3.0 @x8

http://www.anandtech.com/show/5458 [...] g-and-msaa

Reply to FunSurfer

FunSurfer wrote :

There is almost no bottleneck with 7970 on PCIe 3.0 @x8

http://www.anandtech.com/show/5458 [...] g-and-msaa



This is PCI-E 2.0, Ivy bridge has not been released yet.

I would suggest looking at the GTX580 test for x8/x8 and figuring it out from there.

The 7970 is 10 to 20% faster than the GTX580 3GB @ Stock speeds I believe.

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Reply to deadjon

deadjon wrote :

This is PCI-E 2.0, Ivy bridge has not been released yet.

I would suggest looking at the GTX580 test for x8/x8 and figuring it out from there.

The 7970 is 10 to 20% faster than the GTX580 3GB @ Stock speeds I believe.



I don't understand "This is PCI-E 2.0", the bandwidth is 16GB/sec, how can PCI-E 2.0 support that?

Reply to FunSurfer

The difference between x8/x8 and x16/x16 is about 4-5 FPS http://www.tweaktown.com/articles/ [...] index.html


Message edited by sosofm on 02-10-2012 at 02:45:29 PM
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Reply to sosofm

sosofm wrote :

The difference between x8/x8 and x16/x16 is about 4-5 FPS http://www.tweaktown.com/articles/ [...] index.html



Yeah looked at the link from FunSurfer, the difference between a pcie 3.0 x16 vs. x8 is nothing much.

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