I am trying to get a custom resolution to run on my 4k, 60Hz TV. I am mostly working on a Thinkpad that only supports 4k@30Hz via Display Port. I would much rather work on a lower resolution with a higher refresh rate, so I set out to generate a custom modeline (1440p @60Hz). This is necessary since the TVs edid information only forwards 4k and 1080p resolutions.
The first tool I was using is
> cvt 2560 1440 60 # 2560x1440 59.96 Hz (CVT 3.69M9) hsync: 89.52 kHz; pclk: 312.25 MHz Modeline "2560x1440_60.00" 312.25 2560 2752 3024 3488 1440 1443 1448 1493 -hsync +vsync
The left side of everything on my monitor gets replicated on the right side and overlaps a significant part of the right side of the monitor. This overlap is clearly only happening on the monitor level since I can move my mouse "below" the overlap on the right side.
What I did next was trying to understand this webpage about modeline calculation: Modeline Details.
I used the Modelines in my TVs edid and based on that information recalculated the clocks etc. for my specific resolution and my TV. However, it does not work. I cannot move the overlap an inch to the right or left regardless of the value I change in the given Modeline (except of course by changing the resolution itself). I need to be pointed into the right direction to understand where this artefact is coming from and how to resolve it.