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Discussion Starter #1
I recently bought a new mobo: Asus P7P55D-LE.. all happy and well.. good mobo, performance is great etc.. no Xfire in mind untill here.

Now, i got some more cash to spend, and wanna lift my FPS in games up.. So Crossfire came up in my mind. I allready own one XFX 5770 videocard, and would like a 2nd one.. After reading up, i noticed that i have 2 PCI-Express slots, one of them being PCI-Express 2.0 x16 the other one PCI-Express 2.0 x4.

Now, how much of a performance gain would it be to use Xfire on this board, would it be worth it? i have read some comments about PCI-Express 2.0 x4 being only 5% less performance compared with a x16 slot. Is this true?

Could someone explain me, and should i consider going for xfire, or isnt it worth it due to the 16x / 4x

Thank you very much.
 

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I would not. If you want more then sell the HD5770 and get HD5850.
 

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Discussion Starter #3
This is the page i found:

http://www.techpowerup.com/reviews/A...caling/25.html

As u can see here.. on a 5870, which has more bandwith then a 5770.. a 8x has only about 1% less performance then the 16x lane, on PCI-Express 2.0 that is.. the 4x lane has about 5% less performance (on 1680x1050, the res i run) all this on a 5870, which is ofc faster then my 5770.. so according to this graph, i will lose less then 5% performance if i would had a 2nd 16x lane..

Its a little confusing, id like some more opinions on it.. perhaps people that have a Xfire setup running on 16x / 4x

--------

According to Asus.com, my mainboard has following PCI-Express specs:

1 x PCIe 2.0 x16 (single at x16)
1 x PCI Express 2.0 x16 slot (at x4 mode, 2.5GT/s)
2 x PCI Express 2.0 x1 slots (2.5GT/s)
 

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Quote:


This is the page i found:

http://www.techpowerup.com/reviews/A...caling/25.html

As u can see here.. on a 5870, which has more bandwith then a 5770.. a 8x has only about 1% less performance then the 16x lane, on PCI-Express 2.0 that is.. the 4x lane has about 5% less performance (on 1680x1050, the res i run) all this on a 5870, which is ofc faster then my 5770.. so according to this graph, i will lose less then 5% performance if i would had a 2nd 16x lane..

Its a little confusing, id like some more opinions on it.. perhaps people that have a Xfire setup running on 16x / 4x

yeah dude but those results are probably on an X58 board with 4 extra pci-e 2.0 lanes. If i recall correctly the 4 extra lanes on P55 are supplied by the P55 chipset and are pci-e 1.1 or something. but either way it much more of a bottleneck than the 4x on the X58 board.
 

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You lose the x1 slots IIRC when you enable the second x16 on those boards.

EDIT: No, wait, that is AMD 770 chipset.
 

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Quote:


What do you mean by this? sorry for my low knowledge about this kind of stuff... first time Crossfire

dude the bottom line is that it will NOT be worth your time or money to use the 4x slot.
if you really want CF and wont just sell the first 5770 and buy a 5850, just get a P55 that supports SLI/CF
 

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Quote:


Originally Posted by rck1984
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What do you mean by this? sorry for my low knowledge about this kind of stuff... first time Crossfire


If you use the x4 as x4, it'll disable your x1 slots is what was meant.
Honestly, every other P55 mobo's manual I've read with a x4 does this, but yours doesn't seem to have anything about that.

Quote:


Originally Posted by wumpus
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dude the bottom line is that it will NOT be worth your time or money to use the 4x slot.
if you really want CF and wont just sell the first 5770 and buy a 5850, just get a P55 that supports SLI/CF

And this of course...
 

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According to this review page, your board will switch to 8x/8x if you run crossfire:

http://www.elitebastards.com/index.p...7&limitstart=2

There are plenty of expansion slots available here with the P7P55D - The CPU itself provides the support for those two PCI Express 2.0 16x slots (which run in a dual 8x configuration in a multi-GPU configuration), while the P55 chipset itself gives us another two PCI Express 2.0 1x slots and three old-school PCI slots.

Which is totally fine for two 5770's.

Edit: just realized yours is the LE version. But if you check Asus' site for the non-LE version, it has the same specs as yours:

1 x PCIe 2.0 x16 (single at x16)
1 x PCI Express 2.0 x16 slots (@x4 mode, 2.5GT/s)

so I think it's the same 8x/8x in Xfire.
 

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Ok. What about 2x 5770 on a 16x/4x Gigabyte board P55-US3L ? Would it also go 8x/8x mode ?
 

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Discussion Starter #12
Quote:

Originally Posted by brettjv View Post
Edit: just realized yours is the LE version. But if you check Asus' site for the non-LE version, it has the same specs as yours:

1 x PCIe 2.0 x16 (single at x16)
1 x PCI Express 2.0 x16 slots (@x4 mode, 2.5GT/s)

so I think it's the same 8x/8x in Xfire.
The P7P55D will switch to x8 / x8, the -LE does not as far as i know. Which will result in 16x / 4x

Thanks for the straight answers guys, but i am still not 100% sure about everything, ofc i could sell my 5770 and go for a 58xx instead, but id like to hear from some people with experience on a P55 board with 16x / 4x..

After reading tons of websites, loads of people mention that PCI-Express 2.0 16x / 4x performes the same as PCI-Express 1.0/1.1 8x / 8x which is fine for Crossfire, especially on cards like 5770 with less bandwith then a 58xx for example. Even on a P55 board this would be ~5% performance lost..

Sorry for being "stubborn", but the opinions about this matter are different from person to person.. Id like to hear from people that run a 16x / 4x themselfes.. or someone that could explain me about the pci-express 2.0 vs. pci-express 1.0

After some searching i also came across:

16x/4x (CPU/p55) @ 115mhz
http://service.futuremark.com/compare?3dmv=1693433

VS.

8x/8x (CPU) @ 110mhz
http://service.futuremark.com/compare?3dmv=1697343
 

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Discussion Starter #14
Quote:

Originally Posted by Hennessy View Post
So its 17189(16x4x) vs 18752 (8x/8x) ?
According to flat numbers, yes.. Ofcourse there is a difference between 18752 and 17189 but i am not that much of a FPS-sl*t, something like 17189 would be fine for me.

Thats what i ment with opinions are different about this.
PCI-E 2.0 4x, has same bandwith as a PCI-E 1.1 x8, which is quite fine to run Xfire on...

As stated before, it might be better to go for a 5850 instead of 2x 5770's.. but i dont think i can do that right now.

Allready send a mail to Asus as well, if they can explain me a little more about this, waiting for their answer..
 

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It's PCI-e 2.0, the performance drop will be small. If you have the money you can go for it, if you don't like the results you can always sell one or something.
 

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Just so you know rck1984, video cards themselves don't have a 'bandwidth' number that applies to the card as a whole. The amount of bandwidth they require in order to not be bottlenecked on the pci-ex slot is *highly* variable and situation-dependent (i.e. what game, what settings, etc).

In a large majority of cases, the difference in performance between PCI-Ex 2.0 8x/8x lanes and 16x/4x lanes is going to be negligible, sometimes even non-existent. Using 1GB cards helps in your situation, too, because that's plenty of vram for most games, which means that texture swapping with system RAM (which occurs over the PCI-Ex bus) is going to be extremely rare.

There will, however, be the occasion game/setting combo that you'll stumble across (a heavily CPU-dependent game is where it's most likely, since it's really just gpu/cpu communications that's involved here, since you have 1GB of VRAM) where there could be degradation in performance that's 'noticeable' (in the range of, say, a 25% loss in fps vs what you'd get with 8x/8x), but it'll still be faster than a single card, so ...

I say go for it, provided that the 4x slot is indeed 2.0. Frankly though I'd be kinda surprised if your board won't switch to 8x/8x even though it's an LE.
 
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Quote:

Originally Posted by rck1984 View Post
I recently bought a new mobo: Asus P7P55D-LE.. all happy and well.. good mobo, performance is great etc.. no Xfire in mind untill here.

Now, i got some more cash to spend, and wanna lift my FPS in games up.. So Crossfire came up in my mind. I allready own one XFX 5770 videocard, and would like a 2nd one.. After reading up, i noticed that i have 2 PCI-Express slots, one of them being PCI-Express 2.0 x16 the other one PCI-Express 2.0 x4.

Now, how much of a performance gain would it be to use Xfire on this board, would it be worth it? i have read some comments about PCI-Express 2.0 x4 being only 5% less performance compared with a x16 slot. Is this true?

Could someone explain me, and should i consider going for xfire, or isnt it worth it due to the 16x / 4x

Thank you very much.
I actually have this, and the performance increase in some games is definitely fine, but get a single card.
Don't bother with Crossfire unless you're paying over $300 per card.

I get nearly double the fps with Crossfire enabled in Modern Warfare 2 with my P55 LE mobo. I got this before I knew about the 4x lanes and stuff.

Think of it this way, here are 3 scenarios:
1 Card: 100 fps.
2 Cards: 170 fps (1.7x performance)
2 Cards w/ 4x 166.5 fps.

You lose 5% performance on the 2nd GPU.
You're losing 3.5 fps when you're getting fps in the hundreds.
In normal games, you'll be losing under 2.5 fps average...

4x could save you money on your graphics card, but getting a better motherboard and some more powerful cards, or keeping this 16x/4x motherboard and getting one good single gpu. (5870 or maybe gtx 480 if you're looking at Nvidia... just in case...)
 

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Discussion Starter #20
These are constructive answers, thank you very much.

As far as i know, the P7P55D-LE does not switch to 8x / 8x, i mailed Asus and also asked them about this 8x / 8x. Lets see what they have to say about it.

About borrowing another 5770 from a friend, i am affraid no one has a 5770 at this moment, atleast not that i know off. That would be a good way to try it tho..
 
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