I have recently acquired a Dell machine, with one NVS 300 card, and a Quadro NVS 420. The OS is Windows 7 Pro 64-bit w/ 4 GB RAM. I have latest (as of now) drivers
installed and it detects both cards nicely (v 305.93).
The required setup is to have a single (maybe later dual) 22" LEDs connected to the NVS 300 (via DVI), and 4x 55" LCDs connected to the Quadro NVS 420, via 4 DisplayPorts <> HDMI converters. The LED worked of course, the LCDs didn't on the other hand. The NVS refuses to believe there is anything connected to the DP ports. I have googled around and read about EDID sometimes not being transferred through the DP<>HDMI adapters, so I read the EDIDs from my laptop and constructed it in the same format of nVidia's EDID files, loaded it in the nVidia drivers, it read the EDID correctly, but the LCDs are still not working.
I have tried with 4x 22" LEDs (and 2x 22" LEDs on the other card), and they all worked flawlessly. The DP<>VGA adapters works with EDID it seems.
The LCDs are wall mounted and connected of course with HDMI cables (10 mtr gold plated full HD cables), and are capable of full HD 1920x1080 resolution. Tested each separately with a laptop so I know they are working fine.
I am stomped and thirsty for new ideas or comments, any would help !