OpenBSD 7.9 boosts AMD64 CPU core support, adds delayed hibernation and improves scheduler

Theo de Raadt has announced the release of OpenBSD 7.9, which focuses on security, portability, and expanded compatibility. Among the most notable platform changes, AMD64 (x86_64) systems now support up to 255 CPU cores, a significant increase from the previous 64-core limit. Alongside hardware support updates, the scheduler now manages CPU cores that operate at different speeds, offering improved efficiency within heterogeneous hardware setups. Following these core changes, OpenBSD 7.9 introduces delayed hibernation: this power management feature wakes a suspended system after a user-set interval to immediately perform hibernation, helping avoid battery drain while suspended. For hardware stability, AMD64 users benefit from the disablement of Panel Self Refresh in the AMDGPU driver to prevent system hangs specific to the ThinkPad X13 Gen 6. Additionally, mitigations address floating point state leakage on AMD Zen and Zen+ processors, and the AMD PMC driver gains SMU support for better...