是否有实际模式下的x86指令序列可以关闭（不重新启动）机器？我有一台旧计算机，上面还有MS-DOS，对此我很好奇。
这个问题是关于实际模式的，而不是保护模式或64位长模式。
在OSDEV上的本文中，您可以使用ACPI或APM接口。正如您在本文中看到的那样，ACPI似乎过于复杂，而APM更简单。我将报告它们出现在此处的基本步骤：
1）安装检查，查看是否支持APM：
mov ah,53h ;this is an APM command
mov al,00h ;installation check command
xor bx,bx ;device id (0 = APM BIOS)
int 15h ;call the BIOS function through interrupt 15h
jc APM_error ;if the carry flag is set there was an error
;the function was successful
;AX = APM version number
;AH = Major revision number (in BCD format)
;AL = Minor revision number (also BCD format)
;BX = ASCII characters "P" (in BH) and "M" (in BL)
;CX = APM flags (see the official documentation for more details)
2）断开与任何现有接口：
;disconnect from any APM interface
mov ah,53h ;this is an APM command
mov al,04h ;interface disconnect command
xor bx,bx ;device id (0 = APM BIOS)
int 15h ;call the BIOS function through interrupt 15h
jc .disconnect_error ;if the carry flag is set see what the fuss is about.
jmp .no_error
.disconnect_error: ;the error code is in ah.
cmp ah,03h ;if the error code is anything but 03h there was an error.
jne APM_error ;the error code 03h means that no interface was connected in the first place.
.no_error:
;the function was successful
;Nothing is returned.
3）连接到真实模式接口（01H）：
;connect to an APM interface
mov ah,53h ;this is an APM command
mov al,[interface_number];see above description
xor bx,bx ;device id (0 = APM BIOS)
int 15h ;call the BIOS function through interrupt 15h
jc APM_error ;if the carry flag is set there was an error
;the function was successful
;The return values are different for each interface.
;The Real Mode Interface returns nothing.
;See the official documentation for the
;return values for the protected mode interfaces.
4）启用所有设备的电源管理：
;Enable power management for all devices
mov ah,53h ;this is an APM command
mov al,08h ;Change the state of power management...
mov bx,0001h ;...on all devices to...
mov cx,0001h ;...power management on.
int 15h ;call the BIOS function through interrupt 15h
jc APM_error ;if the carry flag is set there was an error
5）最后，将功率状态设置为关闭（03H）：
;Set the power state for all devices
mov ah,53h ;this is an APM command
mov al,07h ;Set the power state...
mov bx,0001h ;...on all devices to...
mov cx,[power_state] ;see above
int 15h ;call the BIOS function through interrupt 15h
jc APM_error ;if the carry flag is set there was an error