Is x16/x4 PCI-E a serious bottleneck for SLI and Crossfire?

[SickBeast]

I'm reading conflicting information. Some reviews are saying that it's only a 5% performance loss by having an x16/x4 PCI-E setup, whereas other sites are saying that it's a much greater performance penalty.

I'm wondering if I would be much better off with an x8/x8 board. I'm going to go with Crossfire or SLI eventually once a hot enough deal crops up on a card.

Is it worth upgrading my x16/x4 board or should I just sit tight and go with a fast single card?

 

[supremor]

Do you want to upgrade to a dual card setup or add another card to the one you already own? Honestly it's better to get the fastest single card you can afford, dual GPU's only make sense if you need more power than any one card can give you or as if its a cheap upgrade to add another card to one you already own. As for bandwith, 8x/8x is obviously better than 16x/4x but as long its PCI-E 2.0 16x/4x should work fine if you're dead set on SLI/CF.

 

[SickBeast]

I just want to max out my system in terms of GPU power eventually. I figure my 2500k at 5ghz can feed a pair of GTX 680s just fine.

For now I just want a fast single card but down the line I think I'll wind up with a pair.

Also, if I find a hot deal on a single card I might just buy two of them and be done with it.

 

[supremor]

Well the last gen of GPUs didn't suffer too much from 16/4x. Not sure how a pair of 680s or equivalent GPUs will fare but personally I wouldnt be comfortable running anything of that calibre at 16/4x. If anything you could always just go for it and run a few benches and and stuff then compare the results to identical or atleast similar setups with 8x/8x to see if you're missing out.

 

[BD231]

http://www.tomshardware.com/reviews/pcie-geforce-gtx-480-x16-x8-x4,2696-5.html

The higher end cards don't do so well in a 4x slot and with cards practically doubling in speed now it'll get worse. You definitely want to be at 8x or better to get the most of your card/cards.

 

[hyrule4927]

Have the same issue with my motherboard, but I think I'm going to pick up a second 6850 regardless. Hoping for the best . . .

If selling wasn't such a hassle, I'd probably just unload the current card and pick up the best thing I could get for ~$250.

 

[maddie]

Then there's this page.

http://www.hardocp.com/article/2010/08/25/gtx_480_sli_pcie_bandwidth_perf_x16x16_vs_x4x4

or this

http://www.techpowerup.com/reviews/AMD/HD_5870_PCI-Express_Scaling/

 

[BD231]

Have the same issue with my motherboard, but I think I'm going to pick up a second 6850 regardless. Hoping for the best . . .

If selling wasn't such a hassle, I'd probably just unload the current card and pick up the best thing I could get for ~$250.

You wouldn't loose any performance with that config, its the higher end cards that are starting to show some difference's. The link I provided simply shows the capabilities of each slot with no CPU bottleneck.

 

[hyrule4927]

You wouldn't loose any performance with that config, its the higher end cards that are starting to show some difference's. The link I provided simply shows the capabilities of each slot with no CPU bottleneck.

Thanks for the info!