The 80286 introduced "Protected Mode" in 1982. It was not popular. The mode was difficult to use, lacked paging, and offered no way to return to real mode without a hardware reset. The 80386, arriving three years later, made protection usable -- adding paging, a flat 32-bit address space, per-page User/Supervisor control, and Virtual 8086 mode so that DOS programs could run inside a protected multitasking system. These features made possible Windows 3.0, OS/2, and early Linux.
Beta 通道规则调整：若用户四个月未安装任何测试版，系统将自动切回公开版更新通道；
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Oct 11 15:56:05 fedora systemd[1]: bootc-fetch-apply-updates.service: Failed with result 'exit-code'.
Here's a concrete example from far return (RETF). The microcode needs to determine whether this is a same-privilege or cross-privilege return, because the two cases require very different handling. Following execution order (not address order):