The funny thing of course is that the Steam Machine has DisplayPort, and you can easily get a DisplayPort to HDMI 2.1 dongle for $20 retail. But they are targeting this being a console, and those are hooked to TVs over HDMI so it seems lame to not have a built-in HDMI port.
This is mostly an academic exercise though. HDMI 2.0 does 4K @ 60hz, and Valve have 4K @ 120hz (with 4:2:0 chroma subsampling) working over it too. Given the CPU/GPU in this machine, it won't be able to push higher than those limits anyway.
This is mostly an academic exercise though. HDMI 2.0 does 4K @ 60hz, and Valve have 4K @ 120hz (with 4:2:0 chroma subsampling) working over it too. Given the CPU/GPU in this machine, it won't be able to push higher than those limits anyway.