If you are using an external video card such Nvidia GTX760, it will disable the onboard graphics for your skylake processor. You could use onboard graphics and external video only if your motherboard BIOS allows both graphics cards at same time.
DirectX 12 is supported on Intel® HD Graphics 530
It works great so far for me with an Intel Skylake 6700k, Asus Z170-A, and an Nvidia 680 GTX. I had to boot with IGFX as default but after then I was able to drive a 4k monitor at 60hz and a secondary 1080 at 60hz off of the Nvidia (possibly another 4k at 60hz off of the Nvidia without the 1080p but I have not tested that yet). This is on Windows 10.
I have also a Skylake 6700k and Asus Z170-A with an Nvidia GTX980ti in use. Though running two monitors with 4k/60hz off the Nvidia, it mere power-usage ramps up to about 80 Watts sitting idle on desktop (Win10). This will be problem when you run into the power-target limit of Nvidia, when wanting maximum processing power for just one 3D-application. Its performance drop when using i.e. two 1080p monitors is negligible though, maybe 1-2% only.
Therefore I've hooked up the secondary 4k-display on the IGFX, but for the 60hz option, I needed to make it the primary adapter in BIOS (Auto, PEG, PCIE, IGFX).
So in this case running two discrete cards, is not only a winner performance-wise, it reduces the comsumption of the whole system by about 50 watts.
Hi all, i described my problem here Problem with dual setup : Intel HD530 (skylake) + GTX970
I can extend my desktop but when i try to use my favourite game it crash at startup. If i disconnect the monitor from hd530 it run well.