The maximum horizontal resolution of the framebuffer for M1/M2 and M3 is limited to 6144 pixels. On the Max/Pro chips it is limited to 7680 pixels (source).
The scaled resolution is rendered in 4x resolutiontimes and then scaled down to the actual screen size. This means that Mac display adapter offers these maximum horizontal resolutions:
- 3K HiDPI scaled resolution on M1, M2 and M3 (3072 * 2 <= 6144 horizontal resolution)
- 4K HiDPI scaled resolution on M* Pro/Max (3840 * 2 <= 7680 horizontal resolution)
If you want to run a higher resolution you'll have to resort to a dummy/mirroring method which can be configured through tools like:
- BetterDisplay - See here for more information.
- SwitchResX