2-way SLI: running at x16 versus x8

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43LMNOP

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For those of you that do not know the difference between the boards:

The UD7 has 4 x PCI Express x16 slots with 2 slots running at x16 and the other 2 running at x8,

The UD4 has 2 x PCI Express x16 slots with one running at x16 and when you use both the slots they both run at x8.

This is a simple question, for running 2-way SLI: How much of a performance increase will you get when you run the cards at x16 versus x8?

I know that there will be a difference, but how much will it be? The thing is, money is not a problem, this is more of a theoretical question than a buying decision one.

Thank you for any replies
wink.gif
 
I've seen a few reviews of people testing whether the nf200 chip running 2x Sli at x16 each lane makes a difference over running Sli at x8 and there was minimal difference.

So with no/v.small gains the nf200 gives, the main question I think is how much do you want to overclock your cpu? If your looking to push it above 4.6Ghz I'd go for the UD7.
 
Yeah, pretty much every review I've seen of the 16x VS 8x debate has given the same answer. We can't really tell the performance increase, it's that low. To the point where it could be mistaken as regular fluctuation.
 
no noticeable difference.

even x4 and x16 there is hardly a difference. maybe about a 5 fps drop MAX. but thats it.

although i would imagine that there is more micro stuttering when in x16 x8 or x16 x4 etc.
 
Scubasage said:
Yeah, pretty much every review I've seen of the 16x VS 8x debate has given the same answer. We can't really tell the performance increase, it's that low. To the point where it could be mistaken as regular fluctuation.
Click to expand...

Got to agree with that,as most modern cards are only just hitting the max of PCIE 1.0 specs tbh,the bandwith still available is HUGE,however being honest does not sell video cards.
 
Agree with the other posters, it takes highly synthetic benchmarks and graphs to notice any difference. In real life you wont notice a thing. But alot of people just get warm and fuzzy when they are running dual 16x.
 
Thank you to all for the response. That was my initial feeling as well.
wink.gif
I also went on a search on the internet and what I found is that it really does not make a difference. But it would be awesome to have both running at x16. Thinking of getting two GTX560, but is wondering if the power consumption will be to much. Will be using the Corsair HX850, think that will be plentiful. At load they will use a lot more power, but then again its the price you pay for having sli.
rolleyes.gif
Still waiting on the new P67 boards, will post something in the build gallery. The longer I wait, the more money I have to spend!
tongue.gif
 
i still find it amazing that there are still companies making sli/xfire boards without 2 x16 slots. my crosshair formula III board from 2009 and it has dual x16 pci
 
KING_OF_SAND said:
i still find it amazing that there are still companies making sli/xfire boards without 2 x16 slots. my crosshair formula III board from 2009 and it has dual x16 pci
Click to expand...

It's really only a limitation of the Intel p67 chipset mate not the board manufacturers, so only the high end boards with an nf200 allow you to do 2 x16 lanes. When the x58 replacement comes along it'll be business as usual
smile.gif
 
Can't wait for the replacement of the X58. Intel must working on something big to counter the new AMD CPU's. The P67 is amazing at overclocking. Yes, I know its easy and for dummies, but you can not take the performance away.
 
I don't know if this helps but here is a comparison in Crysis.

X16

TimeDemo Play Started , (Total Frames: 2000, Recorded Time: 111.86s)

!TimeDemo Run 0 Finished.

Play Time: 40.88s, Average FPS: 48.93

Min FPS: 31.92 at frame 1953, Max FPS: 63.69 at frame 1003

Average Tri/Sec: -46291320, Tri/Frame: -946097

Recorded/Played Tris ratio: -0.97

!TimeDemo Run 1 Finished.

Play Time: 38.04s, Average FPS: 52.58

Min FPS: 31.92 at frame 1953, Max FPS: 65.99 at frame 126

Average Tri/Sec: -49145336, Tri/Frame: -934624

Recorded/Played Tris ratio: -0.98

!TimeDemo Run 2 Finished.

Play Time: 37.93s, Average FPS: 52.72

Min FPS: 31.92 at frame 1953, Max FPS: 70.00 at frame 73

Average Tri/Sec: -49239760, Tri/Frame: -933925

Recorded/Played Tris ratio: -0.98

!TimeDemo Run 3 Finished.

Play Time: 37.93s, Average FPS: 52.73

Min FPS: 31.92 at frame 1953, Max FPS: 70.00 at frame 73

Average Tri/Sec: -49301380, Tri/Frame: -935005

Recorded/Played Tris ratio: -0.98

TimeDemo Play Ended, (4 Runs Performed)

X8

TimeDemo Play Started , (Total Frames: 2000, Recorded Time: 111.86s)

!TimeDemo Run 0 Finished.

Play Time: 41.76s, Average FPS: 47.89

Min FPS: 12.85 at frame 172, Max FPS: 61.70 at frame 125

Average Tri/Sec: -45297092, Tri/Frame: -945871

Recorded/Played Tris ratio: -0.97

!TimeDemo Run 1 Finished.

Play Time: 38.26s, Average FPS: 52.27

Min FPS: 12.85 at frame 172, Max FPS: 63.93 at frame 125

Average Tri/Sec: -48836004, Tri/Frame: -934308

Recorded/Played Tris ratio: -0.98

!TimeDemo Run 2 Finished.

Play Time: 38.21s, Average FPS: 52.34

Min FPS: 12.85 at frame 172, Max FPS: 64.47 at frame 125

Average Tri/Sec: -48831856, Tri/Frame: -933026

Recorded/Played Tris ratio: -0.98

!TimeDemo Run 3 Finished.

Play Time: 38.16s, Average FPS: 52.40

Min FPS: 12.85 at frame 172, Max FPS: 64.47 at frame 125

Average Tri/Sec: -48988468, Tri/Frame: -934818

Recorded/Played Tris ratio: -0.98

TimeDemo Play Ended, (4 Runs Performed)
 
Hribi said:
I don't know if this helps but here is a comparison in Crysis.

X16

TimeDemo Play Started , (Total Frames: 2000, Recorded Time: 111.86s)

!TimeDemo Run 0 Finished.

Play Time: 40.88s, Average FPS: 48.93

Min FPS: 31.92 at frame 1953, Max FPS: 63.69 at frame 1003

Average Tri/Sec: -46291320, Tri/Frame: -946097

Recorded/Played Tris ratio: -0.97

!TimeDemo Run 1 Finished.

Play Time: 38.04s, Average FPS: 52.58

Min FPS: 31.92 at frame 1953, Max FPS: 65.99 at frame 126

Average Tri/Sec: -49145336, Tri/Frame: -934624

Recorded/Played Tris ratio: -0.98

!TimeDemo Run 2 Finished.

Play Time: 37.93s, Average FPS: 52.72

Min FPS: 31.92 at frame 1953, Max FPS: 70.00 at frame 73

Average Tri/Sec: -49239760, Tri/Frame: -933925

Recorded/Played Tris ratio: -0.98

!TimeDemo Run 3 Finished.

Play Time: 37.93s, Average FPS: 52.73

Min FPS: 31.92 at frame 1953, Max FPS: 70.00 at frame 73

Average Tri/Sec: -49301380, Tri/Frame: -935005

Recorded/Played Tris ratio: -0.98

TimeDemo Play Ended, (4 Runs Performed)

X8

TimeDemo Play Started , (Total Frames: 2000, Recorded Time: 111.86s)

!TimeDemo Run 0 Finished.

Play Time: 41.76s, Average FPS: 47.89

Min FPS: 12.85 at frame 172, Max FPS: 61.70 at frame 125

Average Tri/Sec: -45297092, Tri/Frame: -945871

Recorded/Played Tris ratio: -0.97

!TimeDemo Run 1 Finished.

Play Time: 38.26s, Average FPS: 52.27

Min FPS: 12.85 at frame 172, Max FPS: 63.93 at frame 125

Average Tri/Sec: -48836004, Tri/Frame: -934308

Recorded/Played Tris ratio: -0.98

!TimeDemo Run 2 Finished.

Play Time: 38.21s, Average FPS: 52.34

Min FPS: 12.85 at frame 172, Max FPS: 64.47 at frame 125

Average Tri/Sec: -48831856, Tri/Frame: -933026

Recorded/Played Tris ratio: -0.98

!TimeDemo Run 3 Finished.

Play Time: 38.16s, Average FPS: 52.40

Min FPS: 12.85 at frame 172, Max FPS: 64.47 at frame 125

Average Tri/Sec: -48988468, Tri/Frame: -934818

Recorded/Played Tris ratio: -0.98

TimeDemo Play Ended, (4 Runs Performed)
Click to expand...

In all those tests you just posted, the average framerates didn't even drop by 1 full frame per sec. The mins are a lot lower on the 8x. That's the only real difference. Everything else is pretty much the same.
 
I know that TTL likes x16 no matter what. He's pretty stubborn on that topic from what I've gathered. I asked him about it in the past. But yeah, there's almost no difference from the tests I've seen.
 
the bus width and bus speed are two entirely different things.

the reason why the comparisons are almost the same, is that they are hampered by the mobo
 
Ok, so there is hardly a differance. Hands down, if you want the best get the best, but the mid range boards are more accessable for most and this is good news. People get a big grin on their face when they have an SLI rig...
smile.gif
Its one of those things that many dream of having., thats including me!
tongue.gif
 
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