New Apple Silicon M4 and M5 HiDPI Limitation on 4K External Displays
5 hours ago
- #Display Resolution
- #Apple Silicon
- #macOS
- M4/M5 Apple Silicon Macs have a regression that prevents full-resolution HiDPI 4k modes on external 4k displays, unlike M2/M3 models.
- Users must choose between sharp text at reduced screen real estate (3360x1890 HiDPI) or full 4k resolution with blurry text, as 3840x2160 HiDPI is unavailable.
- This limitation stems from the GPU driver's new dynamic framebuffer allocation policy, capping HiDPI backing stores at ~1.75x native resolution, not a hardware constraint.
- Attempts to override via display plists, EDID patching, IOKit registry edits, and private APIs failed, as the restriction is enforced in kernel-space and cannot be bypassed from userspace.
- The issue is confirmed by diagnostic data showing identical DCP capabilities between M2 Max and M5 Max, with the difference lying in mode generation, and a fix would require Apple to adjust the allocation policy.