[oo.viper.oo]

With DVI -> HDMI there is only 3840x2160 @ 30p max.

Just for completeness for other guys reading this (I know you know fritsch :-)):

This particular Intel GPU has two video outputs (relevant for our case):
1. HDMI 1.4 output, which is connected to DVI port on the mainboard's backplate
2. DisplayPort 1.2 output, which is connected to on-board DisplayPort->HDMI 2.0 converter and output of this converter is connected to HDMI port on the mainboard's backplate

So one can connect DVI->HDMI cable to the DVI-out of this mainboard, because this DVI-out is actually HDMI-out. It's HDMI 1.4 though and consequently max. refresh of HDMI 1.4 at 4K resolution is 30p.

Therefore 4K@30p is not some general limitation of DVI->HDMI, but it is limitation of this particular mainboard, because of it's implementation of DVI port.

While this is true, DVI-D only supports a max of around 10Gb/s, which is much lower then the 18Gb/s of HDMI 2.0. The bandwidth limitation also prevents DVI from going above 4k 30Hz.

Whole point of my statement was to highlight the fact that it's not a "DVI-D" what we have on our boards. It was mentioned few times in this thread that we have DVI and it's a misconception. What we have is HDMI 1.4, which just uses physical DVI plug. If it was DVI, it's maximum pixel clock would be 165 MHz and it wouldn't be able to do 4k@30p. However it's not DVI, it's HDMI 1.4 so it's max. pixel clock is 340 MHz and therefore it can do 4k@30p (which requires roughly 255 MHz btw.).

For completeness, to be able to do uncompressed 4k@60p, one needs HDMI 2.0 with it's even higher 600 MHz max. pixel clock and that's why we have the other HDMI 2.0 output on our board (on-board converted from DP).