People that use two video cards in a single system have:
- succeeded in getting it to work when both cards use the same driver,
- not succeeded in getting it to work, when different drivers were needed.
Unfortunately, the Quadro drivers and the GeForce drivers are different, so chances of getting it to work are extremely small if not extinct.
I think your only option is to sell off the FX 3800 and get another GeForce card. You may take a small gamble by getting a GTX 550 or even a GT 520, because AFAIK these use the same driver as the 670. Check that your PSU is up to the task. Or, alternatively, exchange the 670 for a 690, that is only used for 50% by PR, but serves your purpose with DaVinci and only uses a single PCIe slot.
I appreciate the advice.
PSU is Coolmaster 850W and should be golden.
I will install the GTX 670 ...get it working and then consider the second card.
Update and info FWIW
I installed the GTX670 after removing the Quadro FX3800 ( i did not un install the drivers)
New drivers for GTX670 were installed automatically.
System and CS6 Suite ran perfectly.
Color Resolve ran better although not realtime 15-18 fps ( FX heavy grades). Notice still came up that Resolve would prefer to have 2 GPUs.
I decided to see what happened if I put the FX3800 into the spare PCIe slot. ( No monitors connected to it)
I did so...Windows installed it ( I did not neeed or use any additional driver). Device manager recognised two (both) Graphics Adapters.
Da Vinci Resolve recognised it had two GPUs ( one for GUI and one for vidoe processing)
Not much RT performance gain but..a higher spec NVidia card (more cuda and more ram) will sort that in the near future.
I am pleased so far.