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  #1  
Old 05-02-2011, 02:59 PM
Idef1x Limp Gawd, 3.5 Years
 
Status: Idef1x is offline  
16x 4x crossfire with suprising results

This is my first post in here, but I just had something I wanted to share.

Recently I bought my second Asus EAH6950 to crossfire on my Asus P6T. To my disappointment, the two PCI express ports are placed too close together, so the upper card would have a hard time getting ventilated.

I found two crossfire bridges of 100 mm, and placed the second 6950 in the third slot on the mobo. To be even further disappointed, I saw the last slot was a x16 but only with x4 speed.

I ran a 3dmark11 on the system and scored 8336 or something like that. I then tried to place the second 6950 in the second slot, to reach x16 speed, and ran the test again. It scored 8396! Those two scored are virtually the same in my book.

So a P6T crossfire x16 x4 with two Asus EAH6950 is roughly equal to the x16 x16 crossfire.

Any thoughts on this?
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  #2  
Old 05-02-2011, 03:04 PM
g-money Limp Gawd, 6.1 Years
 
Status: g-money is offline  
Not really sure why this is surprising? 16x 16x vs 16x 4x or 8x really is a minor difference and has to have a really hard pushing application to see statistical differences.

Sounds like a win win situation for you.
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  #3  
Old 05-02-2011, 03:12 PM
Idef1x Limp Gawd, 3.5 Years
 
Status: Idef1x is offline  
Quote:
Originally Posted by g-money View Post
Not really sure why this is surprising? 16x 16x vs 16x 4x or 8x really is a minor difference and has to have a really hard pushing application to see statistical differences.

Sounds like a win win situation for you.
Yeah, but I didn't have any experience with crossfire, so never really gave much thought to pci speeds, since it was never an issue. But you are completely right.

But yeah, I was just happy the difference between the setups was so minor just wanted to share if anyone else had the same complications as me.
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  #4  
Old 05-02-2011, 03:18 PM
Raap Gawd, 6.3 Years
 
Status: Raap is offline  
Doesn't this difference increase slightly with resolution?
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  #5  
Old 05-02-2011, 03:29 PM
Matrices [H]ardness Supreme, 11.7 Years
 
Status: Matrices is offline  
A 4x slot card will incur 10% performance hit at 1080p and a 1x slot card will incur 30% hit, IIRC.
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  #6  
Old 05-02-2011, 03:30 PM
XacTactX 2[H]4U, 3.9 Years
 
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Quote:
Originally Posted by Raap View Post
Doesn't this difference increase slightly with resolution?
Yes it does. OP, run any tests or benchmarks that you run at native res. or as high as possible. Check out the difference there too. In [H] Surround evaluation, 8x became a bottleneck of around 10% at 5760 x 1200, but it's usually nothing major with a single display.
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  #7  
Old 05-02-2011, 03:41 PM
Maverick1337 Gawd, 3.7 Years
 
Status: Maverick1337 is offline  
So theoretically would or better to have an 8x8 than a 16x4?
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  #8  
Old 05-02-2011, 03:46 PM
Porter_ [H]ardness Supreme, 7.1 Years
 
Status: Porter_ is offline  
obligatory link to [H] PCIe Bandwidth Performance Article
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  #9  
Old 05-02-2011, 05:14 PM
Michael Turbo n00bie, 3.8 Years
 
Status: Michael Turbo is offline  
What resolution are you gaming at?
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  #10  
Old 05-02-2011, 05:28 PM
Idef1x Limp Gawd, 3.5 Years
 
Status: Idef1x is offline  
Yeah, maybe I should get a full version and do a test on the full resolution. I will try that tomorrow. I am gaming on a 27" 2560x1440.
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  #11  
Old 05-02-2011, 06:02 PM
BababooeyHTJ [H]ardness Supreme, 5.8 Years
 
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How is the actual performance while gaming? Do you notice any strange stutter or anything?
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  #12  
Old 05-02-2011, 06:19 PM
Bunhead n00bie, 3.7 Years
 
Status: Bunhead is offline  
http://www.tomshardware.com/reviews/...ce,2887-9.html
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  #13  
Old 05-02-2011, 07:55 PM
hpokey n00bie, 3.5 Years
 
Status: hpokey is offline  
Yeah it's been a long time that the PCI-E bus has been sitting around waiting to be taxed by anything, and for the most part nothing has managed to live up to doing so. Yet people still pay mad premiums for 16x/16x or 16x/16x/16x,

The bright side is happy little accidents for people like OP. Though the unhappy accident of squashing the two x16 slots together is something I am confounded by quite often when looking at mobos.
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  #14  
Old 05-02-2011, 09:18 PM
hdgamer Gawd, 5.1 Years
 
Status: hdgamer is offline  
I run 2X GTX 480's on my P6T motherboard as well. I've tried all the combinations and found that the performance does not make a difference even when SLI X16 and X4. I'm running a 30" Dell at 2560X1600. Benchmarks are virtually the same. This whole X16 buisness is just to sell you on something you don't really need.
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  #15  
Old 05-02-2011, 09:22 PM
jeremyshaw [H]ardForum Junkie, 5.2 Years
 
Status: jeremyshaw is online now  
Try running both gpu in x4 then
J/k, however it seems to matter at eyefinity surround . Oh well.
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  #16  
Old 05-03-2011, 12:23 AM
noteworthy Limp Gawd, 10.4 Years
 
Status: noteworthy is offline  
Here's my results...

P8P67 LE board running two 6950s in 16x/4x crossfire
http://3dmark.com/3dm11/1042255
P8750

P8P67 WS board running two 6950s in 16x/16x crossfire
http://3dmark.com/3dm11/1085670
P9228
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  #17  
Old 05-03-2011, 04:08 AM
Idef1x Limp Gawd, 3.5 Years
 
Status: Idef1x is offline  
Quote:
Originally Posted by Porter_ View Post
That seems to cover it pretty well. It shown very little performance loss.

Quote:
Originally Posted by BababooeyHTJ;
How is the actual performance while gaming? Do you notice any strange stutter or anything
Nope, no stuttering, aritfacts or anything while gaming. It seems to perform quite alright.

Quote:
Originally Posted by Michael Turbo;
What resolution are you gaming at?
I'm gaming at 2560x1440, but the benchmarks I ran was only with the standard version of 3dmark11. I will perhaps get the full version to do a benchmark at full resolution. But as hardocp concludes in the article posted by Porter_, it doesn't have much impact before very large resolutions - like. 5760 x 1200
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  #18  
Old 05-03-2011, 04:10 AM
Idef1x Limp Gawd, 3.5 Years
 
Status: Idef1x is offline  
Quote:
Originally Posted by noteworthy View Post
Here's my results...

P8P67 LE board running two 6950s in 16x/4x crossfire
http://3dmark.com/3dm11/1042255
P8750

P8P67 WS board running two 6950s in 16x/16x crossfire
http://3dmark.com/3dm11/1085670
P9228
Seems reasonable, even though my scores were even closer together. This is a performance loss of approx 5.5%. Not that bad IMO.
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  #19  
Old 05-03-2011, 10:58 AM
ocellaris [H]ardForum Junkie, 6.8 Years
 
Status: ocellaris is offline  
In related news, I tried Crossfire on a Intel P35 motherboard with 16x/4x PCI Express 1.0 ports and the results were dreadful. Everything I tried except for the Unigine benchmark was slower with Crossfire enabled
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  #20  
Old 05-03-2011, 12:00 PM
Omegas [H]ardness Supreme, 7.8 Years
 
Status: Omegas is offline  
so once you hit a traffic jam, it's almost dead stop.
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