I have a machine with a Quadro FX 580 card (DVI and two Displayport). Attached to it are two 19" Acer screens, which are both (annoyingly) VGA. The first one works perfectly, with a DVI->VGA adaptor.
The second one doesn't work. It's got a VGA cable, which goes into a VGA->DVI converted, which then goes into a DVI->Displayport converter. Initally, I was getting 'Cable Unplugged' on the screen, and it couldn't be seen by Windows or the nVidia control panel. After swapping the VGA->DVI adaptor (which works perfectly on another machine), Windows can now see the monitor. The nVidia panel sees the model and native resolution, but I get a constant 'No Signal' error. Switching to the other Displayport makes no difference.
I suspect that the card is seeing a DVI connection plugged into it (nVididaCP shows the monitor as having a DVI connection), and it only sending out a digital signal because of this. Does anyone know of a solution (other than trying to get a Displayport->VGA adaptor), or of a way to force the card to see it as VGA?
Thanks,
~Dentrasi
Best Answer
Edit: A DVI plug has a combination of digital and analog pins. There are different versions, sometimes pins are missing. A DVI -> VGA converter only channels the analog signal to the right pins, it doesn't (and can't) convert digital to analog. Your card has to provide both Digital and Analog: DVI-I.
A Displayport output is a digital output, it does not contain an analog signal. So the DP->DVI converter can only supply the digital-only DVI-D.
So, sadly, chaining DP -> DVI -> VGA cannot work.
It probably has only 1 A/D converter, that is kind of common for such cards. A D/A converter is relatively expensive. That would mean you can't get it to run 2 analog monitors.