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Radeon 7970: dual 16x vs. dual 8x

Last response: in Graphics & Displays
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February 10, 2012 7:31:45 AM

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 
February 10, 2012 7:44:58 AM

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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February 10, 2012 8:48:06 AM

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.
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February 10, 2012 10:12:01 AM

refillable said:
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...
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February 10, 2012 10:54:58 AM

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

http://www.anandtech.com/show/5458/the-radeon-hd-7970-r...
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February 10, 2012 11:00:31 AM

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

http://www.anandtech.com/show/5458/the-radeon-hd-7970-r...


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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February 10, 2012 11:24:22 AM

deadjon said:
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?
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February 10, 2012 11:57:44 AM

Best answer selected by tha1.
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February 10, 2012 1:09:02 PM

This topic has been closed by Mousemonkey
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