I have an odd behavior on my home system that I was hoping someone could explain or at least provide more puzzle pieces to.
I have a 1440p thunderbolt monitor (Lenovo p27h-10) and a 4k DP monitor. In Macos, the 4k is the primary display. I run it at 3200x1800.
Every manual and tool reports the Lenovo p27h-10 as a 1440p display. But when I use this third-party "Display Menu" app to ask for mirrored displays, the Lenovo P27-h10 runs at 3360x1890. Even though even this app, even while mirroring and the resoluton being listed at 3360x1890 in the tool, the tool doesn't show this resolution in the dropdown as it normally does the "select" res along with other options.
Other than just being surprising, I am interested in what's going on here because it would be nice to run this thing at 3360x1890 when not mirroring, even if it turns out to be at 30hz.
- Text looks fine when it's surprisingly 3360x1890.
- Doing the same mirroring through Settings puts both displays into 1440p
- If the Lenovo is the primary display, putting it into mirroring from the third-party app results in both displays at 1440p
My tentative conclusion as a layman in this stuff is that this mode is somehow supported by the display but not advertised (in EDID?), and some bug in this Display Menu app causes it to try to switch to a mode that it shouldn't try.
- The OSD on the display still says 1440p@60, but "Display Menu" app says 3360x1890.