2 graphic cards at 1 PCIe slot?


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Profile [seti.international] Dirk SadowskiProject donor
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Message 1330499 - Posted: 23 Jan 2013, 21:21:29 UTC

It's possible to connect 2 graphic cards with 1 PCIe slot (using an adapter?)?

Thanks.


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Message 1330512 - Posted: 23 Jan 2013, 22:04:01 UTC - in response to Message 1330499.

No. PCIe is essentially a multi-channel 1 to 1 serial bus. Multiplexing those serial channels is possible with hardware and drivers but I know of no off the shelf product to do so. Only seen in on motherboards to "share" channels between ancillary devices like USB 3 controllers and PCIe ethernet chips.
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Message 1330514 - Posted: 23 Jan 2013, 22:08:28 UTC

Alternatively, yes. But make sure you have deep pockets with plenty of $$$ in them.

A few moments with a search engine and the keywords "PCIe expander" turns up products like:

http://www.cyclone.com/products/expansion_systems/600-2707.php

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Message 1330516 - Posted: 23 Jan 2013, 22:19:46 UTC
Last modified: 23 Jan 2013, 22:23:00 UTC

GT(x) x9x usually have two GPU's for one PCIe Slot

GTX690 GTX590 GTX490(well almost:-) GTx295 etc...

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Message 1330578 - Posted: 24 Jan 2013, 3:04:18 UTC - in response to Message 1330499.

Is it possible? Yes.

Should you do it? No.



The best way to get two cards in one PCIe slot is to do what Tom told you, get one card that has two gpu on it. It will cost you premium, probably going to need to get a new power supply to power that beast, but that is the smart way to get two gpu in one PCIe slot.
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Message 1330589 - Posted: 24 Jan 2013, 3:52:18 UTC - in response to Message 1330516.
Last modified: 24 Jan 2013, 3:57:34 UTC

GT(x) x9x usually have two GPU's for one PCIe Slot

GTX690 GTX590 GTX490(well almost:-) GTx295 etc...

Yes those cards have two GPUs but card either splits the x16 into x8 pairs or it multiplexes the x16, switching when required.
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Message 1330629 - Posted: 24 Jan 2013, 6:04:26 UTC - in response to Message 1330589.

GT(x) x9x usually have two GPU's for one PCIe Slot

GTX690 GTX590 GTX490(well almost:-) GTx295 etc...

Yes those cards have two GPUs but card either splits the x16 into x8 pairs or it multiplexes the x16, switching when required.


Which is the same thing that would happen even if you did physically hook up two cards to one slot.
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Message 1330674 - Posted: 24 Jan 2013, 9:13:26 UTC - in response to Message 1330629.

GT(x) x9x usually have two GPU's for one PCIe Slot

GTX690 GTX590 GTX490(well almost:-) GTx295 etc...

Yes those cards have two GPUs but card either splits the x16 into x8 pairs or it multiplexes the x16, switching when required.

Which is the same thing that would happen even if you did physically hook up two cards to one slot.

But at least the power supply requirements will be properly accounted for.

If you tried to mount two separate cards in a single slot with a passive 'Y' cable or similar, and both cards tried to draw the maximum 75W that PCIe is specified for, then you'd fry the motherboard.

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Message 1330738 - Posted: 24 Jan 2013, 16:27:50 UTC

You might need to look for something such as this.
http://www.supermicro.com/a_images/products/Accessories/RSC-R2UT-2E8R.jpg
Depending on your needs a different riser might be what you need. Here is their full list.
http://www.supermicro.com/support/resources/riser/riser.aspx

There are several ways to do this. The main issue I would see is mounting the cards in the setup.


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Message 1330905 - Posted: 24 Jan 2013, 21:13:04 UTC
Last modified: 24 Jan 2013, 21:14:31 UTC

My tip, is possible, but don´t try do that, is safer and cheap buy a better MB with more slots or build a second host.

Even the factory made double GPU´s have some limitations (i have few 590/690 so i know wath i´m talking) imagine a "band-aid" solution.

We do something similar by ussing a PCI-extensors in order to put more GPU´s on the same MB (but still 1 GPU per slot), works but in the end all goes to complicated and the entire system easely crashes, and when works all the PCI-e slots works extreamely slow, so the actual performance decrases exponentialy.
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Message 1330961 - Posted: 24 Jan 2013, 23:00:59 UTC

This works, 16x PCIe Video Card in 1x PCIe slot, However, you may ruin your board, and you can forget about any warranty afterwards...

I speak from personal experience.

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Message 1331071 - Posted: 25 Jan 2013, 7:03:26 UTC - in response to Message 1330499.

There is also this adaptor
http://www.ebay.com/itm/PCI-32bits-to-PCI-E-express-16X-riser-card-adapter-/320693561785?pt=LH_DefaultDomain_0&hash=item4aaad369b9

Lets you connect a PCI-e card into an old PCI slot. It means the card only communicates at PCI speed, but for SETI work that's not a fatal problem. If I remember right another cruncher has tried them and found less than 10% performance loss.

Of course putting the lid back on the PC may be an issue, but shoe horning 2 cards into one slot is going to cause that sort of issue anyway.

Ian

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Message 1331079 - Posted: 25 Jan 2013, 7:50:16 UTC - in response to Message 1331071.
Last modified: 25 Jan 2013, 7:54:09 UTC

There is also this adaptor
http://www.ebay.com/itm/PCI-32bits-to-PCI-E-express-16X-riser-card-adapter-/320693561785?pt=LH_DefaultDomain_0&hash=item4aaad369b9

Lets you connect a PCI-e card into an old PCI slot. It means the card only communicates at PCI speed, but for SETI work that's not a fatal problem. If I remember right another cruncher has tried them and found less than 10% performance loss.

Of course putting the lid back on the PC may be an issue, but shoe horning 2 cards into one slot is going to cause that sort of issue anyway.

Ian


I could confirm, this works i try before, but you made your 16x card run in a 1x slot, and yes not a totaly dissaster if you run SETI but some misterious "hangs" happens when running, never realy find why, all my tests point in the direction of hidden mechanical incompatibilites and/or electric faulty conections (like some spikes in the PCI-e slot due the high frequency), normaly cleared after reboot.

If you want to try just keep in mind if your GPU drain power (not all do that) from the PCI-e there is a 75W limit on all devices, or you will literaly "melt" your 12V connectors on your MB.
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