Thought I would offer some feedback on the new Nvidia GTX 780 with 6GB of GPU RAM (double the original card). The gaming community weren't too enthusiastic about this card saying that the extra RAM would have no effect on game play, but looking at the demands of DaVinci it seemed like the extra RAM would help. Unusually I became an early adopter and bought the EVGA branded card from Overclockers when it was released. Here are my findings.
Prior to installing the new card I had an Nvidia GTX 570 (1.28GB) with an old Nvidia Quadro card. I have a Windows i7 3.6GHz processor with an Asus P9X79 motherboard (not the Pro) and 32GB of RAM, so not a slow machine.
With this setup HD playback was fine until I added NR or sharpen when playback was 1 or 2 frames per second. As soon as I changed the project settings to UHD the screen filled with shash and I got the message that I was out of memory. I could render out in 4K but it was slow and I could not see the results processing.
With the GTX780 installed in PCIEX16 slot 1 and the GTX 570 in slot 2. Thanks to a tweet form @rohit_bmd I tried removing the GTX570 as he suggested this card may slow things down. He was right and all speeds have increased by 2-3 fps with just the GTX 780 in place.
In Media and Edit modes the 4K (well UHD) footage from the BMPC plays back at 21 - 23 fps and audio is smooth. This is only on a 1920x1080 computer monitor - I don't have an external 4K monitor yet.
In Color mode even without adding any grading, NR or sharpening the playback occurs in bursts with a slight pause (less than a second) between each one. DaVinci reports that playback speed is varying between 10fps and 13fps. Adding sharpen lowers this rate to 8-10 fps. Not ideal but at least I can see what the effect the colour correction on a full 4K image. For noise reduction this makes a big difference. I have not received any out of memory pop-ups.
Delivery (rendering) is very quick and I can now see the pictures as they are processed.
The computer RAM is barely being troubled by Resolve and 16GB would be more than enough but the CPU peaks at around 75% usage on playback so a fast processor is recommended.
An added bonus of the new card is the speed of After Effects which is loving the massive CUDA core boost.
Conclusion: For the money I think this is an excellent upgrade for DaVinci if you are wanting to work with 4K footage. It surpasses what would be expected from the DaVinci configuration guide from this setup. I think that if I added another GTX 780 6GB card I would be close to running at 25fps in Color mode.
Hope this helps others looking at buying this card. EVGA are offering a step-up if you have an older EVGA card.