Second graphic card not detected ? | Gtx 680 / Gtx 980 ti |

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Second graphic card not detected ? | Gtx 680 / Gtx 980 ti |

Hello !
I've been trying to install a gtx 980 ti in addition of the gtx 680 that I had installed on the macpro; I have a 850w corsair psu that is operationnal with a jumpstarter on the atx connector to externally power up the gtx 980 ti. I'm using El capitan OS, and all corresponding cuda and nvidia webdrivers have been installed. Problem is, when connected to the gpu, the power supply doesn't seems to turn on (I initially thought it was the psu that was faulty but I had it changed and checked, strangely it turns on normally when on it's own and stops when connected to the gpu.)
The main problem is that the computer doesn't detect the additional graphic card, despite the fact that the additional card lights up with the fans working when I boot the computer. I also tried swapping the cards from slot one to two without success.
Any ideas ?

Mac Pro, OS X El Capitan (10.11.3)

Posted on Feb 13, 2016 10:20 AM

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Answer 1

BDAqua

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239,225 points

Feb 13, 2016 11:02 AM in response to Supranutz

Have you tried just the 980 by itself?

680 needs 195 Watts, 980 needs 250 Watts.

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Answer 2

Allan Jones

Level 9

68,714 points

Feb 13, 2016 11:02 AM in response to Supranutz

.

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Answer 3

Supranutz Author

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Feb 13, 2016 12:06 PM in response to BDAqua

980 ti needs 600 watts, and just by itself with the psu everything is working correctly, which is not the case when the graphic card is connected to the computer..

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Answer 4

BDAqua

Level 10

239,225 points

Feb 13, 2016 12:19 PM in response to Supranutz

600 Watts is the recommended Minimum for the PSU...

Thermal and Power Specs:

92 C Maximum GPU Tempurature (in C)

250 W Graphics Card Power (W)

600W or greater Recommended System Power (W)**

6-pin + 8-pin

http://www.geforce.com/hardware/desktop-gpus/geforce-gtx-980-ti/specifications

680...

Thermal and Power Specs:

98 C Maximum GPU Tempurature (in C)

195 W Maximum Graphics Card Power (W)

550 W Minimum System Power Requirement (W)⁵

Two 6-pin

http://www.geforce.com/hardware/desktop-gpus/geforce-gtx-680/specifications

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Answer 5

Supranutz Author

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Feb 13, 2016 12:31 PM in response to BDAqua

Yes, 250watts for the gtx 680 is provided by the computer, and the 600+watts for the gtx 980 ti is provided by an external 800w power supply.
I did another test after having the external power supply successfully starting up with the graphic card only, not only the power supply did not started (again) when I connected the graphic card to the computer, but the card fans also started being really loud so I had to quickly shut the computer down..

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Answer 6

BDAqua

Level 10

239,225 points

Feb 14, 2016 10:10 AM in response to Supranutz

Ah, an extra external PSU, didn't see that before.

Might it be some uncommon voltage between the PSU supplying power or ground to the PCIe bus on the card & the external PSU supplying the bulk of the power to the card?

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Answer 7

Feb 15, 2016 4:40 AM in response to Supranutz

If you haven't already done so visit http://www.macvidcards.com/do-i-need-an-additional-power-supply.html and then read the articles linked from their about using an additional power supply for a video card. Maybe that will suggest something.

Note: The 600w rating is based on the assumption that the power supply has to power the computer as well as the video card. In this case as it will only power a video card which only needs in this case 250w it is if anything over specified. As a comparison the Mac Pro built-in power supply is rated at 980watts.

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