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8x/8x Crossfire

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April 9, 2010 7:10:29 PM

Im going to buy a micro atx gaming case. But the only modercards that i found have 8x/8x when i use 2graphic cards (crossfire), is this going to be a bottleneck with 2x5870cards in my case? Is there any micro atx-cards which supports 2xcards with x16 crossfire?

More about : crossfire

a b V Motherboard
April 9, 2010 7:38:16 PM

Why not buy a bigger case so you don't face any motherboard restrictions? It's not like they cost a hell of a lot more.

Also, I don't think there is any single-GPU card on the market than can saturate an 8x slot -- only double-GPU cards like the 5970 or GTX295. The 5870 might get close, but unless I am mistaken you should not notice much difference, if any.

I'd honestly be more concerned about heat in a setup like that. Crossfired 5870s and (I assume) a high-end CPU could turn a small case into a nice little hellbox if your cooling isn't up to snuff.
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April 9, 2010 7:48:17 PM

capt_taco said:
Why not buy a bigger case so you don't face any motherboard restrictions? It's not like they cost a hell of a lot more.

Also, I don't think there is any single-GPU card on the market than can saturate an 8x slot -- only double-GPU cards like the 5970 or GTX295. The 5870 might get close, but unless I am mistaken you should not notice much difference, if any.

I'd honestly be more concerned about heat in a setup like that. Crossfired 5870s and (I assume) a high-end CPU could turn a small case into a nice little hellbox if your cooling isn't up to snuff.


I really want a small computer. Is there any micro atx card with 16x crossfire?
The cooling is good in this case, and it fits 2x5870 cards.
The modercard have 2 16x pci-e ports but when i use them with crossfire they become 8x, why?
So the modercard is a bottleneck with the x8 crossfire?
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a b V Motherboard
April 9, 2010 8:06:39 PM

there will be a 1% bottleneck with x8 crossfire, you would not notice it whatsoever. Listen t the Taco, for his information is accurate!
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a c 297 V Motherboard
April 9, 2010 8:35:14 PM

Hi newcomer and welcome to the Tom's hardware forum.

Honestly, a mATX is a junk for the rig that I think you want build. You won't see a big difference between x16 and x8, but the space in the mobo and case is important too. More, if you can install a sound card, or something else.
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a b V Motherboard
April 9, 2010 8:39:19 PM

spel565 said:
I really want a small computer. Is there any micro atx card with 16x crossfire?
The cooling is good in this case, and it fits 2x5870 cards.
The modercard have 2 16x pci-e ports but when i use them with crossfire they become 8x, why?
So the modercard is a bottleneck with the x8 crossfire?


I honestly haven't heard of any that are 16x/16x. The micro atx ones are overwhelmingly 8x/8x or 16x/4x

The reason most boards downgrade to 8x/8x when using two cards is because the two PCIe x16 slots are actually sharing the same set of 16 data lanes. Putting in a second card means you're trying to cram twice as much data through the same amount of overall bandwidth. If it sounds like cutting corners in the manufacturing process, that's exactly what it is -- but it keeps the costs down, and 99% of people won't notice any difference because 8x is still plenty.

Boards with true 16x/16x have 32 lanes, which obviously makes them more expensive and more complicated to manufacture. I'm not even sure if they can fit it all on a micro board. But again, unless you're using a pair of dual-GPU cards (2xHD5970 or 2xGTX285) you should not notice a bottleneck.
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a b V Motherboard
April 9, 2010 8:46:23 PM

ummmm, micro ATX LGA1366 boards
LGA1366 mATX

EDIT: though i agree with the above, for a setup with $800 in GPU's, just go for ATX and a decent sized Mid ATX tower
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April 9, 2010 8:56:08 PM

capt_taco said:
I honestly haven't heard of any that are 16x/16x. The micro atx ones are overwhelmingly 8x/8x or 16x/4x

The reason most boards downgrade to 8x/8x when using two cards is because the two PCIe x16 slots are actually sharing the same set of 16 data lanes. Putting in a second card means you're trying to cram twice as much data through the same amount of overall bandwidth. If it sounds like cutting corners in the manufacturing process, that's exactly what it is -- but it keeps the costs down, and 99% of people won't notice any difference because 8x is still plenty.

Boards with true 16x/16x have 32 lanes, which obviously makes them more expensive and more complicated to manufacture. I'm not even sure if they can fit it all on a micro board. But again, unless you're using a pair of dual-GPU cards (2xHD5970 or 2xGTX285) you should not notice a bottleneck.

But it look like its a bit different fps @ http://www.tomshardware.com/reviews/crossfire-meets-pci...
And someone @ http://www.tomshardware.co.uk/forum/252455-15-crossfire...
Said "It depends on which cards you till run in the 8x/8x configuration.... any of the brand new cards will be bottlenecked and you will not see all the performance the cards have to offer... I know they did testing on the new 4850 and found it was bottlenecked. I can't find the article ATM but Im sure you can search for it.

My advice is unless you are going to use some slightly older cards just put the money into one big monster. This way you will never have to worry about scaling issues some games have with crossfire. "


mindless728 said:
ummmm, micro ATX LGA1366 boards
LGA1366 mATX

EDIT: though i agree with the above, for a setup with $800 in GPU's, just go for ATX and a decent sized Mid ATX tower
'

Money doesnt matter, size does.
If performence are kinda same why chance?
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a b V Motherboard
April 9, 2010 9:02:11 PM

well, the amount of cooling matters, and the amount you can move in a large case is a lot more than a small one, also a small case with get hotter quicker

ie with a mATX tower, you might get 2 x 120mm fans
in a good mid tower, you can get 8

and why does size matter other than you prefer a small computer

also those people were talking about pci-e 1.0, not 2.0 (which is twice as fast)
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April 9, 2010 9:20:09 PM

mindless728 said:
well, the amount of cooling matters, and the amount you can move in a large case is a lot more than a small one, also a small case with get hotter quicker

ie with a mATX tower, you might get 2 x 120mm fans
in a good mid tower, you can get 8

and why does size matter other than you prefer a small computer

also those people were talking about pci-e 1.0, not 2.0 (which is twice as fast)


They are talking about pci-e 1.0?

why does size matter other than you prefer a small computer.. huh?

This computer have 3x120mm fans and 3x80mm
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a b V Motherboard
April 9, 2010 10:04:38 PM

mindless728 said:
ummmm, micro ATX LGA1366 boards
LGA1366 mATX


Wow, it totally didn't even occur to me that they would make X58 boards in that size. For some reason, I always thought of them as full-sized ATX standard. Where the hell have I been. I guess that solves the problem.


spel565 said:
why does size matter other than you prefer a small computer.. huh?


That's a perfectly good question ... as in, it sounds like you're voluntarily setting yourself up for some serious headaches in order to gain something that doesn't really matter.
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a c 216 V Motherboard
April 9, 2010 10:15:04 PM

I remember reading that with the 57xx series there was no effect.....5850 a few % and at the 5870 it was approaching 4-5%....I expect this may increase a bit as game devs start to do more with DX11 features and really start to pump pixels.
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a b V Motherboard
April 9, 2010 10:20:47 PM

JackNaylorPE said:
I remember reading that with the 57xx series there was no effect.....5850 a few % and at the 5870 it was approaching 4-5%....I expect this may increase a bit as game devs start to do more with DX11 features and really start to pump pixels.


I had thought I read that the 4-5% loss with the 5870 was for the P55 chipset, but with x58 it dropped to almost nothing again.

Of course, I could be entirely wrong, since I am not as well-versed in what's going on with 1366 boards, on account of there's no way I'm going to be able to afford a system with one any time soon.
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April 9, 2010 10:26:29 PM



Omg problem solved i found a crossfire 16x/16x crossfire support card for micro atx, thanks to mindless728. (http://ca.asus.com/Product.aspx?P_ID=6i86Hj0lGriFHfY9)
Sound perfect.

And this is going to be a nice small computer with dual 5870, 920, 6gb ram etc.
Im going to have 3x120mm fans and 3x80mm fans, an h50 cpu cooler, and gpu coolers. So i think its going to be kinda ok temperature?

thanks guys, case closed.

Any comments btw?
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a b V Motherboard
April 9, 2010 10:34:29 PM

The toms bench you provided is comparing pci-e 1.0 spec at 8x to pci-e 2.0 at 16x. I have no idea why you would want to compare the two in that way. but if you converted pci-e 2.0 bandwith to pci-e 1.0 you would be comparing a 8x bus to a 32x bus. no exactly fair.

an 8x pci-e 2.0 equals 16x pci-e 1.0 so it's hard to imagine any SINGLE gpu solution maxing that out in a dual card setup.
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a b V Motherboard
April 10, 2010 1:23:32 AM

PsyKhiqZero said:
The toms bench you provided is comparing pci-e 1.0 spec at 8x to pci-e 2.0 at 16x. I have no idea why you would want to compare the two in that way.


You simply don't know what you're talking about.

In fact, half of the guys in this thread are speaking out of ignorance. The Tom's Hardware P55 CrossFire articles were all run at PCIe 2.0 for both x8 and x16, and

get this:

High-end Micro ATX and high-end ATX are pretty much the same thing, quality and engineering wise. You can get a top Micro ATX board such as the Rampage II Gene, with two full-bandwidth PCIe 2.0 x16 slots, that pretty much stomps on big boards such as the P6T Deluxe.

You don't have to take my word for it, try reading some reviews instead.

To the OP: If you want dual PCIe 2.0 x16, look at X58 (Intel) or 790FX (AMD) motherboards. Those remain the gold standard no matter how many slots the board has.

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a b V Motherboard
April 10, 2010 2:22:34 AM

Ok sorry I guess I got a bit confused. but the charts do show all the x8 x8 configs with 1.0a and the x16 x16 configs with 2.0

HD2900 XT (512 MB) CF PCIe 1.0a x8x8 779.2 100.0
HD2900 XT (512 MB) CF PCIe 2.0 x16x16 904.8 116.1
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a b V Motherboard
April 10, 2010 2:31:51 AM

PsyKhiqZero said:
Ok sorry I guess I got a bit confused. but the charts do show all the x8 x8 configs with 1.0a and the x16 x16 configs with 2.0

HD2900 XT (512 MB) CF PCIe 1.0a x8x8 779.2 100.0
HD2900 XT (512 MB) CF PCIe 2.0 x16x16 904.8 116.1


You must be, those aren't P55 stats. Here's your sign:

http://www.tomshardware.com/reviews/p55-pci-express-sca...

And, if you want to see a workaround for the x8/x8 (PCIe 2.0) performance loss, check this one:

http://www.tomshardware.com/reviews/p55-crossfire-nf200...
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a b V Motherboard
April 10, 2010 2:46:54 AM

I don't wish to beat a dead horse. However your links are not what I was commenting on. Here is the link that the OP posted.
http://www.tomshardware.com/reviews/crossfire-meets-pci...

again notice how the chart shows that the x8 x8 rigs are running in pci-e 1.0a and the x16 x16 rigs are running in 2.0.
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a b V Motherboard
April 10, 2010 3:12:13 AM

PsyKhiqZero said:
I don't wish to beat a dead horse. However your links are not what I was commenting on. Here is the link that the OP posted.
http://www.tomshardware.com/reviews/crossfire-meets-pci...

again notice how the chart shows that the x8 x8 rigs are running in pci-e 1.0a and the x16 x16 rigs are running in 2.0.


And here I thought you were replying to capt_taco, who referred to the P55 articles. If this is the case, someone needs to tell the OP to quit using irrelevant stuff and start looking at some more realistic articles, like the one capt_taco referred to and I later linked.
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April 10, 2010 6:50:34 PM

Best answer selected by spel565.
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a b V Motherboard
April 10, 2010 10:17:48 PM

Crashman said:
OMG, you picked an "I haven't heard of it" response for best answer? Has anyone actually read the reviews?

http://www.tomshardware.com/reviews/system-builder-mara...
http://www.tomshardware.com/reviews/rampage-gene-lanpar...


Well, that came as a surprise to me too ... I'd really never even considered whether they made 16x/16x boards that small, because I really don't know why you'd want to build a machine like that in such a small case.

Ahh well. At least the main thing is, I think we've basically established that it will work for him without too much trouble regardless.
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a b V Motherboard
April 10, 2010 11:55:25 PM

capt_taco said:
Well, that came as a surprise to me too ... I'd really never even considered whether they made 16x/16x boards that small, because I really don't know why you'd want to build a machine like that in such a small case.

Ahh well. At least the main thing is, I think we've basically established that it will work for him without too much trouble regardless.


It all fits!



Really, I can't see why so many people like those enormous trash-can cases when a more efficient design doesn't cost much more.
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a b V Motherboard
April 11, 2010 12:00:40 AM

Crashman said:
It all fits!

http://media.bestofmicro.com/,H-M-211882-3.jpg

Really, I can't see why so many people like those enormous trash-can cases when a more efficient design doesn't cost much more.


i don't like those huge cases, but one that small is going to tend to have thermal problems, i have a Rosewill mid tower and it works fine (and its light)
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a b V Motherboard
April 11, 2010 3:20:10 AM

Crashman said:
Really, I can't see why so many people like those enormous trash-can cases when a more efficient design doesn't cost much more.


I'm not really a fan of the super-giant ones. But I have had more than my fill of trying to use my big fat hands to squeeze components into a tight space ... and then some cable keeps falling and getting in the way and you have to stop and tie it off ... and then it turns out your SATA ports are oriented in the opposite way you'd want them, and the only way to make it work is to have a hard drive cable bending back on itself ... and then the PCIe power cables won't fit in your cards unless you twist them an odd way ... and then one of them doesn't go all the way in and you pull it out to do it over, and you bang your hand on the side of the case and give yourself a nice irritating cut on your knuckle...

Things like that. I just prefer a case that makes it easy to take things in and out, and has obvious places to tuck cables away, etc. And with a pair of GPUs like that in such a tight box, the heat would worry me regardless.
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a b V Motherboard
April 11, 2010 3:55:51 AM

wow crashman what case is that?
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a b V Motherboard
April 11, 2010 5:08:04 AM

PsyKhiqZero said:
wow crashman what case is that?


SilverStone SG03.
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a b V Motherboard
April 11, 2010 7:17:32 AM

Just out of curiosity ... where is the CPU in that setup, and what's cooling it? Not doubting that it works, but it just doesn't look like there's a place for much more than a CPU laying flat in that picture.
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a b V Motherboard
April 11, 2010 7:32:38 AM

capt_taco said:
Just out of curiosity ... where is the CPU in that setup, and what's cooling it? Not doubting that it works, but it just doesn't look like there's a place for it in that picture.



You know one of the links points to that system...

It's an i7-920, and it's too warm with the stock cooler, but that's probably partly due to the PSU fan pulling against the CPU fan. I recommended the same setup to someone else using a low-profile 120mm cooler and an upward facing fan last week.

This sink fits, but the fan is a little too thick:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Here's a 20mm-thick fan that will fit:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Mounting the fan in the "suck" direction allows the PSU to assist cooling.
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a b V Motherboard
February 23, 2012 12:49:15 AM

This topic has been closed by Mousemonkey
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