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how do pci-e speeds work?

Tags:
  • PCI Express
  • Crossfire
  • Motherboards
Last response: in Motherboards
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April 5, 2013 5:24:16 AM

I have this motherboard:
http://www.gigabyte.com/products/product-page.aspx?pid=...
running an i5 750 2667mhz OC @ 3.6ghz, 4gb 1600mhz RAM.

Expansion Slots
*1 x PCI Express x16 slot, running at x16 (PCIEX16) (The PCIEX16 slot conforms to PCI Express 2.0 standard.)
*1 x PCI Express x16 slot, running at x4 (PCIEX4)
2 x PCI Express x1 slots
3 x PCI slots
Multi-Graphics Technology
Support for ATI CrossFireX™ technology

I have a Radeon HD 7870 tahiti LE on its way now and am wondering if a 2nd would be worth it? I'm not sure whether it would scale both PCIE slots back to x4 and make it not worth it?

Thanks for any help you can give!

More about : pci speeds work

a b V Motherboard
April 5, 2013 5:34:12 AM

A 2nd would not be worth it. That mobo is only designed for 1 gpu to go in the PCIE 2.0x16 slot. The 2.0x4 would be a bottleneck for the card.
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a b V Motherboard
April 5, 2013 6:56:32 AM

I second Wanderer's opinion; that is not quite the right board for crossfire, even though the specs say that crossfire is supported.

OTOH, I recently read an article showing that slower slots had very little effect on card performance. Wish I could link you to it...
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a b V Motherboard
April 5, 2013 7:37:38 AM

You're right wyoming, there is usually very little. My thinking in saying not to try cf with that mobo is why spend ~$500 on gpus to only get ~65-75% of the performance you should.
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a c 75 V Motherboard
April 5, 2013 10:08:32 AM

As the others have said for SLI or Xfire that board wouldnt be the best option for you. While the cards can take a small drop by running both cards at 8x/8x on PCI-E 2.0 but to run one at 4x is really cutting into its bandwidth. The reason for this limited number of lanes is that the "5" series boards are limited to about 20 total lanes of support from the chipset. While some companies add additional controllers (high end boards if you can still find them) to get more for the most part you are stuck at 20 total.
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