smcleodNew Apple Silicon M4 and M5 HiDPI Limitation on 4K External Displays
https://smcleod.net/2026/03/new-apple-silicon-m4-m5-hidpi-limitation-on-4k-external-displays/
Send it to Tim Cook email. It worked for me fixing DisplayPort DSC bug. After Catalina, later MacOSes lost ability to drive monitors at higher than 60Hz refresh.
Apple support tortured me with all kinds of diagnostics, with WontFix few weeks later. Wrote email and it got fixed in Sonoma :)
https://egpu.io/forums/mac-setup/4k144hz-no-longer-available...
Thank you
No, it didn’t get fully fixed.
Fucking with DP 1.4 was how they managed to drive the ProDisplay XDR.
If your monitor could downgrade to DP 1.2 you got better refresh rates than 1.4 (mine could do 95Hz SDR, 60Hz HDR, but if my monitor said it could only do 1.2, that went to 120/95 on Big Sur and above, when they could do 144Hz HDR with Catalina).
I would be absolutely unsurprised if their fix was to lie to the monitor in negotiation if it was non-Apple and say that the GPU only supported 1.2, and further, I would be also unsurprised to learn that this is related to the current issue.