Video bandwidth is precious. In particular the HDMI standards seem to lag in providing the bandwidth I need. Partly because I run old hardware. One silly wast of bandwidth is blanking intervals. That mattered for CRTs since steering the electron beam took time. It should not matter for LCDs. CVT-RB (Coordinated Video Timings - Reduced Blanking) is a standard for reducing the blanking intervals. It sometimes makes the difference for supporting UltraHD. <https://en.wikipedia.org/wiki/Coordinated_Video_Timings#Bandwidth> I haven't yet fiddled with this. Perhaps it is currently optimal on my systems. But I have had mysterious troubles getting UltraHD working on some systems. The linux cvt(1) command has a flag --reduce: Create a mode with reduced blanking. This allows for higher frequency signals, with a lower or equal dotclock. Not for Cathode Ray Tube based displays though. But I don't think that command is used in my (automatically generated) configurations. Does Linux automatically know when to use CVT-RB? If so, how does it know? If not, how do you tell it?