Dual GPU - help.

[Cesar R]

This is the first time I am using two different GPUs on a workstation and I am having a little problem.

I have a GTX 660 Ti 4GB from evga and a GTX 640 2 GB also from evga.

 

The 660 had two power connector while the 640 do not.

I have two questions,

 

1 . I noticed the 660 will run without the power connected. This makes me wonder what excactly are those power connectors feeding then ?

 

2. When the 660 is connected with the power cables, I am unable to get a display signal on the 640.

I ultimately want to use the 640 to drive the windows display and the 660 as a secondary card to use as a GPU rendered while using iray (active shade)

 

Can someone please help me sort these things out?

 

PS: I am starting to think I should have just gotten 2 GTX 640 cards.

[Dimitris Tolios]

What PSU are you using?

The 660ti will need the aux power when being stressed. If you are doing nothing on it (it idles), the 75W or w/e from the pcie slot are enough.

There is no way you are using those 2x cards in your workstation running the 470s and now the PSU is not enough!

Edited February 2, 2013 by dtolios

[Cesar R]

no I dont think so. The PSU came with the workstation (Lenovo from the other thread) I looked it up and it is a 610W unit.

I think that should be enough considering the 640 does not use additional power.

 

Both cards work and are recognized in windows and 3dsmax. However I am unable to make the 640 give me video while the 660 is plugged in.

Do you think the 660 takes power away from the 640 ? doesnt make sense to me though.

[vijay_1279]

i dont know

but

the gpu' s may be belongs to same family

like gtx 640 x gtx640 or

660x660

 

other wise different clock speed will not works

its my opt?

[Dimitris Tolios]

The only reason to have identical cards is to SLI (physically link them with a bridge etc, and say, one card is dealing with odd lines, the other with even lines etc). Late AMD cards can Crossfire even with non-identical cards, just need to be of the same architecture / compatible to do so.

[Cesar R]

they work fine, I just can't get the 640 to be my primary. Its almost as if windows 7 defaults and like the GPU with the external power.

[Dimitris Tolios]

they work fine, I just can't get the 640 to be my primary. Its almost as if windows 7 defaults and like the GPU with the external power.

 

I believe you can select your prefered primary adapter through the nVidia control panel:

 

3D Settings> Manage 3D Settings > Global Settings Tab > Preferred Graphics processor drop down menu.

[Francisco Penaloza]

Yes you should check your drivers first, there you can control what card is the primary one , now sometimes BIOs also control this, so you may check that too.

GTX are power hunger, 670 w may be in the short side, depending how many hard drives and Dvd's drives you also have in your PC.

I had several isues with 2 Nvidia cards in the past, but updating the drivers and cheking options in BIOs should work.

On the Card website you'll see how much power your card will need at full load, if you plan to use one of those card for I Ray you'll need enough power for your CPU and GPU at render time, I Ray uses both.