I know modern card architecture doesn't support this out of the box, but what is the actuall problem of forwarding a once-rendered frame to another card for output? Sureley DMA transfers PCIe->RAM->PCIe nowaday are fast enough to saturate 60fps at 4K?
While transfers have improved a lot the amount data needed for 4K60 with HDR is about 18Gbps. There's no way that doesn't have an impact.
I had a crazier setup in the past with the Intel i7-8809G APU: it had an AMD iGPU for desktop connected to the display, nVidia eGPU for games and the Intel iGPU for video encoding.
Of course there is additional latency due to frame copying, but I can’t notice it in practice.
> We want to render applications on the more powerful card and send the result to the card which has display connected.