Cuda and SLI

Questions and Answers : GPU applications : Cuda and SLI
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NuclearRage

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Message 864018 - Posted: 10 Feb 2009, 6:29:09 UTC

I have looked but couldn't find any solid answers
I have an AMD x2 6000(3.1 brisbane)
MSI K9N2 Platinum mb
2x XFX 9800gt's in sli

latest nvidia drivers and vista 64 fresh install

I load up seti and test it out

problem is , it only sees 1 gpu not the 2 that are installed
i have disabled sli and still only sees 1 gpu

thought it was an error , so i looked at hardware monitor and sure enough one of my gpu's is 10-15 deg C hotter, so its only running on one...

will it work on both , is there a setting that i missed?


exact specs:
K9N2 Platinum SLI 750a MS-7374 v1.2
AMI Ver 3.2
AMD 64x2 6000 Brisbane G2 3.1ghz 65nm
Corsair Dominator DDR@1066 (4x2gb) 5-6-6-18-25
2xXFX 9800gt pvt98gydlu 181.20 SLI
Ultra lsp750 3.3v28a 5v32a (200w com) 1x12v45a540w
Maxtor 500gb7200rpm sata port 1
Lite on DVD burner sata port 2
Lite dvdrom ide & liteon dvd/rw ide both on ide1
Vista 64 Prem SP1

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Duner

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Message 864023 - Posted: 10 Feb 2009, 6:58:41 UTC
Last modified: 10 Feb 2009, 7:00:21 UTC

After you disable SLI in Nvidia control panel, you need to "activate" your second monitor. You'll either need to hook it up to another monitor or use a dummy VGA plug. Then go into monitor properties. I'm not sure how this works in Vista, but in XP just right click the desktop and select properties. Chose to "extend my windows desktop" to the second monitor/videocard.

Voila, you now have two monitors up and running and will see two video cards in windows, temp monitoring software, rivatuner for overclocking, and of course SETI will use process 2 CUDA units.

Oh and if you don't have two monitors, most monitors will have 2 inputs. I just used one input for each video card.
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NuclearRage

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Message 864028 - Posted: 10 Feb 2009, 7:08:52 UTC - in response to Message 864023.  

lemme see if i have this, turn on second monitor that is physically plugged into 2 gpu? I have dual mon set up now , but with sli or what not both are plugged into the same physical card ....
you saying plugg another monitor into the second physical card?
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Zydor

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Message 864040 - Posted: 10 Feb 2009, 10:50:33 UTC
Last modified: 10 Feb 2009, 10:52:09 UTC

CUDA does not currently recognise SLI - you have to disable SLI for it to recognise both cards, because the software will not operate across the strap you have physically connecting the SLI cards (the straps are motherboard dependent and each differ from board manufacturer to board manufacturer).

If you want to play a game that needs more than card (and few REALLY do in truth, depends on eye candy wishes), nip in NVIDIA Manager and enable SLI (CUDA still crunches but only on one card whilst you play a game - no bad thing from the game viewpoint), when you have finished, disable SLI and you are back to CUDA on both cards. You'll see in BOINC Manager two tasks when the cards are non SLI, and only one task running when SLI is enabled, so its easy to check you have it "right".

Slight pain but not exactly onerous. When its disabled, the CUDA software sees both (or four or three or whatever is in your SLI groupings) as separate cards, and is a happy bunny. I understand from background chit chat they will bring in SLI on future CUDA enhancement that will prevent the need to manually switch.

Regards
Zy
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Message 864059 - Posted: 10 Feb 2009, 13:42:02 UTC - in response to Message 864040.  

CUDA does not currently recognise SLI

Correction. SLI means that you have two or more graphics cards working as one, with a single output. BOINC will recognize all the cards, but it will only use one card due to it being used in SLI mode. Seti CUDA will then only work on one card.

NuclearRage wrote:
problem is , it only sees 1 gpu not the 2 that are installed
i have disabled sli and still only sees 1 gpu

Did you exit BOINC and restart it?
Jord

According to Giorgo of the Ancient Astronaut Theorists I do not help with tech questions via private message. He's right: please use the forums for that.
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Duner

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Message 864087 - Posted: 10 Feb 2009, 15:35:06 UTC - in response to Message 864028.  

lemme see if i have this, turn on second monitor that is physically plugged into 2 gpu? I have dual mon set up now , but with sli or what not both are plugged into the same physical card ....
you saying plugg another monitor into the second physical card?


Correct. This is not a BOINC issue. It's a windows thing. When you disable SLI, Windows "disables" the second card. You will need to restart BOINC after this as well.
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NuclearRage

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Message 864398 - Posted: 11 Feb 2009, 19:49:34 UTC - in response to Message 864087.  

ok , got it running

had to hook 2nd monitor to 2nd gpu card
disabled sli and then restarted
now boinc sees and uses both card , temp monitor confirms both cards are cooking up numbers

So for others who may have this issue , a 2nd monitor or something like it , 2nd input to same monitor , but there has to be a monitor hooked to both cards , mmaybe a kvm switch would work also.. then of course diable sli , you dont have to remove the sli bridge , just disable thru NCPL and then your set

seems to be crunhing w/u in 5-10 minutes walltime , so far no error , just a few w/u reported at 58 and then validated at 42 so your actual scores seem to be lower than your claimed credit.

system spec again to help anyone else who has this issue

K9N2 Platinum SLI 750a MS-7374 v1.2
AMI Ver 3.2
AMD 64x2 6000 Brisbane G2 3.1ghz 65nm
Corsair Dominator DDR@1066 (4x2gb) 5-6-6-18-25
2xXFX 9800gt pvt98gydlu 181.20 SLI
Ultra lsp750 3.3v28a 5v32a (200w com) 1x12v45a540w
Maxtor 500gb7200rpm sata port 1
Lite on DVD burner sata port 2
Lite dvdrom ide & liteon dvd/rw ide both on ide1
Vista 64 Prem SP1

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Duner

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Message 864474 - Posted: 12 Feb 2009, 0:47:40 UTC - in response to Message 864398.  

Glad you got it up and running.

You don't always need a second monitor or cable. I mentioned a "dummy VGA plug" in my first post. If you google it, it's basically a DVI to VGA converter with a resister that makes the Card feel like it's hooked up to a monitor.

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Profile popandbob
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Message 864561 - Posted: 12 Feb 2009, 4:22:15 UTC

Also a side note to others who may read this... XP doesn't require a dummy plug :)

~Bob


Do you Good Search for Seti@Home? http://www.goodsearch.com/?charityid=888957
Or Good Shop? http://www.goodshop.com/?charityid=888957
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Message 867485 - Posted: 21 Feb 2009, 0:37:23 UTC

Thanks
Maurus Balmer
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Questions and Answers : GPU applications : Cuda and SLI


 
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