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PCIe 2.0 @ x8/x8 vs x16/x6

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January 3, 2010 3:12:19 PM

I bought a SLI AM3 motherboard and knew it was x8/x8 when I bought it. My question is though is it worth it to return the board and get another that has SLI speeds at x16/x16? The price would be almost double what I payed for the x8/x8 board. I will be getting one GTX 260 for now, then getting another down the road once I can get the card and a new PSU. Do these cards even use all the bandwidth of PCIe 2.0? Would I really see any performance difference? How big of a performance difference is there between x8/x8 and x16/x16. I have read in the past its usually negligible.

More about : pcie x16

January 3, 2010 3:17:10 PM

P.S. I am going to run games at 1440x900 in DX9 for a while as well. DX10 when I get Win7, but resolution will stay the same.
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January 3, 2010 5:50:28 PM

Maziar said:
For that resolution there is no need for SLI/CF,a single powerful card can handle games on that resolution fine,however the difference between dual 16x and dual 8x isn't much in games,here is a good review:
http://www.tomshardware.com/reviews/crossfire-pci-expre...


Well found a cheap monitor that is 19" with 1680x1050. What about at those resolutions?
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January 3, 2010 11:11:04 PM

pcman09 said:
Well found a cheap monitor that is 19" with 1680x1050. What about at those resolutions?


Pretty much the same. A powerful single card can run most games at 1680x1050. Only games like crysis at very very high settings could ever make you buy a second gpu.

Now when you hit resolutions like 1900x1200 is when CF/SLI can really be considered.
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January 3, 2010 11:22:52 PM

warmon6 said:
Pretty much the same. A powerful single card can run most games at 1680x1050. Only games like crysis at very very high settings could ever make you buy a second gpu.

Now when you hit resolutions like 1900x1200 is when CF/SLI can really be considered.


Thanks. SLI is pretty far down the road though. Don't have the $$$ for it right now, not after buying the monitor and my new PC. Will stick with one card, and maybe down the road in about a year I can upgrade the MOBO, or get another card within a few months along with a new PSU. Will play it by ear.
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a c 136 V Motherboard
January 4, 2010 6:27:14 AM

pcman09 said:
Well found a cheap monitor that is 19" with 1680x1050. What about at those resolutions?

Still a single fast card can handle that resolution fine
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a c 216 V Motherboard
January 4, 2010 5:14:34 PM

I had another very good link like the one Maz posted which showed the results when they forced a x16 card to run at x 8 and x4 ...was pretty significant loss, but like Maz's they were for older chipsets.....posted in yesterday in an other thread but can't find now.

I have seen an article which addressed this issue with newer chipsets but damned if I can find it. As i recall tho, you really had no issues up to around a GT 250 / ATI 5750 which THG reports "provides good 1920x1200 performance in most games".....or maybe the 260 / 5770. Above that , performance differences were observable.
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January 4, 2010 5:18:16 PM

+1 To the above.
Your GTX 260 is more than powerful enough for anything 1650x1080 and below.
It even does a pretty decent job at 1920x1200.

As to the specific question, 8x/8x vs 16x/16x, you are looking at around a 2-7% Difference in Performance with 5870 class GPU's.
I would say that, if you need SLI in the future, your motherboard can handle it just fine.
No reason to spend twice as much on a full 16x/16x motherboard.
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January 4, 2010 5:35:16 PM

Is a review like This what you are looking for Jack?
Techpowerup tested a 5870 @ PCIe 2.0 1x, 4x, 8x and 16x with a 3.8Ghz i7.

I was quite surprised by the results.
At 1x the 5870 still had, on average, ~75% of its performance of the 16x results.
Even in newer, more texture hungry games, 1x performed for the most part at higher than 50% of the 16x results.
Most of the games only showed minimal losses at 4x link speed.
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January 5, 2010 12:11:23 AM

outlw6669 said:
Is a review like This what you are looking for Jack?
Techpowerup tested a 5870 @ PCIe 2.0 1x, 4x, 8x and 16x with a 3.8Ghz i7.

I was quite surprised by the results.
At 1x the 5870 still had, on average, ~75% of its performance of the 16x results.
Even in newer, more texture hungry games, 1x performed for the most part at higher than 50% of the 16x results.
Most of the games only showed minimal losses at 4x link speed.


I see as with that chart you listed, with a 5870, which is way above my budget, at x8/x8 it operated at 99% which is very minimal performance loss. So x16/x16 upgrade wouldn't be worth the double $$$ price tag. Since SLI at 1680x1050 doesn't even show significant performance boosts until you get to 1920x1080 resolutions, which I will never play at, probably won't even SLI now. Thanks all so much! You have all been a huge help!
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January 10, 2010 5:35:33 PM

outlw6669 said:
Is a review like This what you are looking for Jack?


I am rembering one that had the same kinda thing done but with twin cards. My addled brain remembers the 5870 being at the border of significance but don't remember if it as 5870 and above to a hit or 5870 and below was no significant hit.
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