"Crossfire Support" - But is it actually capable?

alexdrans · 19 Feb 2011 at 21:20

I bought the Gigabyte GA-880GA-UD3H motherboard today, and it has crossfire support, but only comes with a PCI-E 16x and a PCI-E 4x. Is this truly capable of crossfire?

For now I only want a single GPU, but I may go multiple GPUs in the future. I'd rather have a single NVidia than a single AMD (Linux support) but I'm willing to play around more to get the drivers to work if I can use dual-GPUs for gaming in W7.

stulid · 19 Feb 2011 at 21:33

No, its a bodge way of doing it.

wildman · 19 Feb 2011 at 21:54

I thought to get best performance you needed 2 run but at x 16 so you woul dneed a board like http://www.overclockers.co.uk/showproduct.php?prodid=MB-398-AS&tool=5

well thats what I have been reading, I admit to being new to this so I could be wrong

stulid · 19 Feb 2011 at 21:58

wildman said:
I thought to get best performance you needed 2 run but at x 16 so you woul dneed a board like http://www.overclockers.co.uk/showproduct.php?prodid=MB-398-AS&tool=5

well thats what I have been reading, I admit to being new to this so I could be wrong

Hardocp had this test - http://www.hardocp.com/article/2010/08/23/gtx_480_sli_pcie_bandwidth_perf_x16x16_vs_x8x8/

And many others, which showed the difference is not a lot between 16/16 and 8/8

and the chipsets that do crossfire right are

8/8 - 790GX/890GX

16/16 - 790X/FX/890FX

RJC · 19 Feb 2011 at 21:59

I think the difference between dual 16x and 8x is around 2-5% ~

Hopefully someone can confirm.

Steves1982 · 19 Feb 2011 at 22:14

Yeah, it's less than 5%, about 2-3fps I believe. Not worth worrying about really, I have mine running in x8/x8 and I can't tell the difference.

iBSOD · 19 Feb 2011 at 22:16

8/8 you don't lose any frames (maybe 0.1 if you're unlucky).

4/4 you could lose about <10fps with 480's.

It only scares people because it looks like x8 has half the bandwidth of x16.

chaparral · 20 Feb 2011 at 02:34

iBSOD said:
It only scares people because it looks like x8 has half the bandwidth of x16.

Think it more to do with people forget or don't know that PCI-E 2.0 slots has double the bandwidth compared to PCI-E 1.1 slots

PCI Express 1.0a
In 2003, PCI-SIG introduced PCIe 1.0a, with a data rate of 250 MB/s and a transfer rate of 2.5 GT/s.

PCI Express 1.1
In 2005, PCI-SIG introduced PCIe 1.1. This updated specification includes clarifications and several improvements, but is fully compatible with PCI Express 1.0a. No changes were made to the data rate.

PCI Express 2.0
PCI-SIG announced the availability of the PCI Express Base 2.0 specification on 15 January 2007.[10]
The PCIe 2.0 standard doubles the per-lane throughput from the PCIe 1.0 standard's 250 MB/s to 500 MB/s. This means a 32-lane PCI connector (x32) can support throughput up to 16 GB/s aggregate. The PCIe 2.0 standard uses a base clock speed of 5.0 GHz, while the first version operates at 2.5 GHz.

PCIe 2.0 motherboard slots are fully backward compatible with PCIe v1.x cards. PCIe 2.0 cards are also generally backward compatible with PCIe 1.x motherboards, using the available bandwidth of PCI Express 1.1. Overall, graphic cards or motherboards designed for v 2.0 will be able to work with the other being v 1.1 or v 1.0.