2x PCIe 2.0 x16 - (32 lanes) mobo ?


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Message 857284 - Posted: 24 Jan 2009, 19:39:52 UTC
Last modified: 24 Jan 2009, 20:08:40 UTC

I would like to have a mobo which have 3x PCIe 2.0 x16 GPU slots.

For an Intel Core2 Extreme QX6700. Socket 775.
This mean min. 1066 MHz (4x 266 MHz) FSB and 800er RAM.

I looked around, but now I'm confused and have questions..


If I buy a nVIDIA-Chipset on the mobo, it's possible to have a SLI-connection for the GPUs?

With the GPUs I get SLI-connectors also.
This will not needed?
[This is only (limited) for 2 GPUs?]

If I buy for example a mobo with Intel-Chipset these SLI-connectors are needed?


If I can read:
2x PCIe 2.0 x16 and 1x PCIe x16 and 3-way-SLI.. what?? ..the one slot have only PCIe 1.0 x16 !?!


If I have 3 GPUs with PCIe 2.0 x16 then I would like to have also the performance of PCIe 2.0 x16 ! :-)
(With and without SLI)


Which mobo you can recommend?


Thanks a lot!


BTW.
Is the QX6700 @ 2.66 GHz fast enough to support 3x GPUs if they crunch CUDA?
Or I need also a new CPU?


What's about the architecture?
An AMD-platform would have better performance/connection?
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Message 857289 - Posted: 24 Jan 2009, 19:48:53 UTC

You wont get one with 3 PCIe2 x16 sockets
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Message 857294 - Posted: 24 Jan 2009, 19:56:41 UTC

I think tri-SLi is limited to x4 slots? Not sure for a fact since I've never thought about putting a system like that together. And Nvidia chipsets at one time where the only way to get SLi.
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Message 857296 - Posted: 24 Jan 2009, 19:59:21 UTC - in response to Message 857289.

You wont get one with 3 PCIe2 x16 sockets


Why?

How it's possible to have a 3-way-SLI-connection with 2x PCIe 2.0 x16 and 1x PCIe 1.0 x16 slots with 3x PCIe 2.0 x16 GPUs?

So the max. is 2x PCIe 2.0 x16 and PCIe x16 on one mobo.
So if I insert 3x GPUs, one is only with PCIe 1.0.
And the third GPU will lose performance..
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Message 857299 - Posted: 24 Jan 2009, 20:02:20 UTC - in response to Message 857294.
Last modified: 24 Jan 2009, 20:03:49 UTC

I think tri-SLi is limited to x4 slots? Not sure for a fact since I've never thought about putting a system like that together. And Nvidia chipsets at one time where the only way to get SLi.


To my knowledge.. I read the last days a lot.. ;-) [but don't know if it's right] ..you can have 3-way-SLI with 3x x16 slots..

But I'm confused, why one of the three have only PCIe 1.0 ..


EDIT:
But if I insert the GPUs without SLI.. the third is only at PCIe 1.0 also..
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Message 857321 - Posted: 24 Jan 2009, 20:23:08 UTC

Check the photo and thread for this extreme machine.
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Message 857323 - Posted: 24 Jan 2009, 20:24:47 UTC
Last modified: 24 Jan 2009, 20:32:57 UTC

i believe the most you could have in an x38/x48 motherboard is 3 pcie running at x16, x8 and x8 as they have a total of 32 pcie lanes. this however, really doesnt matter if you are using sli as from what i understand, you will basically only be using the x16 on the first card
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Message 857332 - Posted: 24 Jan 2009, 20:39:46 UTC

This is from the Nvidia web site.

The nForce 790i Ultra SLI MCP provides support for 2-way, 3-way and earth-shattering Quad SLI.
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Message 857342 - Posted: 24 Jan 2009, 21:29:59 UTC - in response to Message 857284.

I would like to have a mobo which have 3x PCIe 2.0 x16 GPU slots.

Sutaru, maybe a dumb question, but what do you want SLI for? If you want it for gpu crunching, then you don't need SLI and you don't even want it.

If you put 3 gpu's in SLI then the stuff just behaves as 1 big gpu. It's not 3 times as fast, though, so for crunching you're better off with a non-sli setup anyway (if you're cards are sufficiently fast, anyway).

Things get different when considering playing games, of course :-)

Regards,
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Message 857369 - Posted: 24 Jan 2009, 22:46:33 UTC - in response to Message 857296.

You wont get one with 3 PCIe2 x16 sockets


Why?


Because the current PCIe specification doesn't allow for more than 32 lanes.
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Message 857713 - Posted: 25 Jan 2009, 18:11:00 UTC
Last modified: 25 Jan 2009, 18:12:33 UTC

I renamed the title of this thread from:
3x PCIe 2.0 x16 - mobo ?
to:
2x PCIe 2.0 x16 - (32 lanes) mobo ?




O.K., here we go..

I say you my thoughts.. ;-)

I would like to build a GPU-crunching-rig.

With two GTX 260 Core 216 GPUs.. [yes, I know.. take a GTX 295 GPU.. but it'll make to much noise.. ;-)]

I thought to buy a mobo with two PCIe 2.0 x16 slots.. (32 lanes)

I would like to have a less W TDP CPU..
The GPUs will take enough W.. ;-)

For example the AMD Athlon x2 5050e have only 45 W TDP.

Modellbezeichnung ADH5050DOBOX Taktfrequenz 2x 2600 MHz Level 1 Cache 2x 128 KB Level 2 Cache 2x 512 KB Befehlssätze MMX, SSE, SSE2, SSE3, AMD64, Cool'n'Quiet, NX-Bit, Pacifica, Presidio Bustakt 2000 MT/s Prozessorkern Brisbane EE, 65 nm Bemerkung G2 Stepping max. Leistungsaufnahme 45 Watt Core Spannung 1,15 Volt - 1,25 Volt I/O Spannung 3,3 Volt Bauform OPGA Sockel AM2


Is this CPU/Mobo-combi fast enough to support 2x GTX 260 GPUs?

But, I searched and didn't found a mobo with 2x PCIe 2.0 x16 (32 lanes) for AMD-CPUs.
Only for Intel socket 775.

So.. there are some reasons, that there are no AMD-mobos with 32 lanes, or I didn't found it to now?


Thanks a lot!
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Message 857716 - Posted: 25 Jan 2009, 18:21:03 UTC

http://www.overclockers.co.uk/productlist.php?groupid=701&catid=5&subid=806

there are some at the very least
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Message 857722 - Posted: 25 Jan 2009, 18:47:09 UTC

Latest trend says 6x pci-e slots :-)

http://www.dignova.com/story/80413/ASUS-P6T-WS-PRO-and-P6T6-WS-Revolution-with-6x-PCI-E-x16-slo.html

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Message 857779 - Posted: 25 Jan 2009, 21:11:26 UTC


Hey.. or is this now the finally solution..??


The min. requirement for the mobo because of the GPU.. [GTX 260 Core 216]
In the manual: PCIe or PCIe 2.0 mobo with x16 GPU-slot

So this is PCIe x16 or PCIe 2.0 x16 slot.


I found after reading some hours in the Inet..
PCIe 1.0 x16 = PCI 2.0 x8

Correct?


So if I find a mobo with 2x PCIe 2.0 x8 I will not reduce the calculation speed.


Correct?


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Message 857821 - Posted: 25 Jan 2009, 22:49:34 UTC

Correct. PCI-e 2.0 has twice the bandwidth of 1.0, and the upcoming 3.0 will be twice the bandwidth of 2.0.
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Message 862279 - Posted: 5 Feb 2009, 11:28:15 UTC - in response to Message 857821.

I think this is where we run outta bandwidth, even with triple channel DDR3, to power more than two dual PCIe 3.0 16lane channels fully. That would be equivalent to 16 PCIe 1.0 16Lane channels.
Please tell me Im wrong so I can get one for my next machine :)


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Message 862288 - Posted: 5 Feb 2009, 13:15:02 UTC

Just a side note to be clear ...

AT THIS TIME, using SLI will mean that you will only run one GPU core of all those installed. There are changes in the wings that will fix this, but they are not here yet.

How the use of SLI will speed up or not affect operation is unclear. What I mean to say is that if they change the APi so that SLI can be left enabled the programs may not actually be able to use the full capability of the cards in that mode.

WIthout SLI attached I have an Intel MB with two PCI-e slots and two GTX 295 cards and happily keep 4 tasks in flight at the same time ...

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Message 862314 - Posted: 5 Feb 2009, 15:05:10 UTC


@ Paul D. Buck

How you disabled the SLI-mode with your GTX 295?

A teammate got his GTX 295 now and can only crunch with one GPU..

He said, he disabled also SLI.. but maybe in a wrong area?

You took the nVIDIA-software to disable?

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Message 862319 - Posted: 5 Feb 2009, 15:21:20 UTC


What are the min. requirements for SLI-mode?

The chipset on the mobo.. AND.. SLI-cable connected?
Or only the SLI-cables?

For example my mobo have the AMD® 790FX chipset and 4* PCIe 2.0 x8 slots.
So I could take 4* GTX 2xx and connect with the cables this four GPUs and would have one big GPU?
[for now not crunching.. ..but maybe in future? ;-)]

Or is the max. for SLI three GPUs?

And the max. for ATI it's four GPUs? [CrossFire]

The specs from the mobo:
• Equip with 2 or more PCIe x16 slots, ATI CrossFire Ready.
• The ultimate multi-GPU performance gaming platform.
• Provides 2.7x faster performance than single graphic card solution.

So the last line it's with 3 ATI-GPUs I guess.. so 3 connected GPUs slow down the crunching speed, or? [If it'll be possible in future]

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Message 862384 - Posted: 5 Feb 2009, 18:56:18 UTC - in response to Message 862314.
Last modified: 5 Feb 2009, 18:59:54 UTC


@ Paul D. Buck

How you disabled the SLI-mode with your GTX 295?

A teammate got his GTX 295 now and can only crunch with one GPU..

He said, he disabled also SLI.. but maybe in a wrong area?

You took the nVIDIA-software to disable?


Never hooked it (SLI) up ...

I have two GTX 295 cards in the i7 BOx and I am running BOINC Manager 6.5.0 which has some issues but runs the cards correctly ... oh, and driver version 181.22 ... though using the Nvidia control panel causes BSOD ... so I see 4 GPU tasks in flight at all times with from one to four pending ...

On the GPU Grid forums the 6.6.x versions all develop problems sooner or later ... from not fetching work at all to screwing up LTD to the point where the projects are not properly called for work.

{edit}
If you enable SLI mode you get one big honkin GPU, but BOINC does not use the other cores at all... so in my case I would have 3 idle GPU cores ... when Nvidia does some changes to the API the SLI mode should make the card one big GPU and you MAY see (in my case) one GPU core with 4 times the performance.

The question is if the applications can really use all that parallelism or most of it would go to waste. In other words in SLI mode you would be only able to see an effective improvement of about 2.7 over the use of single cores on each task... meaning you would still be better off running as four single GPU cores.

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