How can shutdown the PC with Assembly 16 bits in boot mode?

Question

I wrote a small bootloader that i write in a Diskette, the bootloader is working fine, i write a function to reboot the PC, but i can't shutdown the PC, i try a lot but i've just got an infinite beep song from the speaker. I'm in boot mode, so windows interruptions doesn't work. How can i do it? I'm compiling with NASM and write in diskette with Rawriter.

I had tried a code that i see here in Stackoverflow, but it doesn't works.

MOV     AX,5307
MOV     BX,0001
MOV     CX,0003
INT     15

And i tried that another too

   mov ax, 0x1000
    mov ax, ss
    mov sp, 0xf000
    mov ax, 0x5307
    mov bx, 0x0001
    mov cx, 0x0003
    int 0x15

Answer 1

How far you do want to go with this?

Because shutting down a computer is chipset specific, the hardware programming interface has never been standardized.
However a software interface has been standardized, actually two have been: Advanced Power Management (APM) and Advanced Configuration And Power Interface (ACPI) .

While the first is really easy and it is the one you are using, it is very very old (in computer industry years). I have made a simple boot program that use APM to shutdown the computer. It does all the things pedantically in the proper way.
With Bochs it works. On real hardware (tested on 3 laptops) it doesn't and prints the error code A which means No APM service found .
This seems to suggest that the APM interface is no longer supported, this didn't surprise me to be honest I was expecting it and the converse would have.

So you are left with the ACPI , now unless you are really familiar with it I simply suggest you to not dig into that (rather if your is a specific solution get your chipset datasheet) as it is quite elaborate, and has specific terminology and it handle the whole aspect of power management.
You would have to find and parse various tables, interpret AML code sequences, setup a proper environment, it will take a long long time.

The closest thing to a shutdown without APM or ACPI is the well known

cli
hlt

instruction pair.

If you are interested in the APM boot program to give it a try, here it is

BITS 16
jmp 07c0h:WORD __START__

__START__:
  mov ax, cs
  mov ss, ax
  xor sp, sp
  push cs
  pop ds
  push WORD 0b800h
  pop es

  mov ax, 03h
  int 10h



  ;^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^     
  ; \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \
  ;  v   v   v   v   v   v   v   v   v   v   v   v   v   v   v   v   v

  ;Check APM service is present
  mov BYTE [error], 'A'  

  mov ax, 5300h
  xor bx, bx
  int 15h
  jc .err
  inc BYTE [error]
  cmp bx, 504dh
  jne .err

  ;^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^     
  ; \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \
  ;  v   v   v   v   v   v   v   v   v   v   v   v   v   v   v   v   v

  ;Connect RM interface, compatibility mode APM 1.0
  inc BYTE [error]

  mov ax, 5301h
  xor bx, bx
  int 15h
  jc .err

  ;^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^     
  ; \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \
  ;  v   v   v   v   v   v   v   v   v   v   v   v   v   v   v   v   v

  ;Switch to APM 1.1+
  inc BYTE [error]

  mov ax, 530eh
  xor bx, bx
  mov cx, 0101h
  int 15h
  jc .err
  inc BYTE [error]
  cmp al, 01h
  jb .err

  ;^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^     
  ; \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \
  ;  v   v   v   v   v   v   v   v   v   v   v   v   v   v   v   v   v

  ;Enable APM
  inc BYTE [error]

  mov ax, 5308h
  mov bx, 01h
  mov cx, 01h
  int 15h
  jc .err

  ;^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^     
  ; \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \
  ;  v   v   v   v   v   v   v   v   v   v   v   v   v   v   v   v   v

  ;Engage APM
  inc BYTE [error]

  mov ax, 530fh
  mov bx, 01h
  mov cx, 01h
  int 15h
  jc .err

  ;^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^   ^     
  ; \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \
  ;  v   v   v   v   v   v   v   v   v   v   v   v   v   v   v   v   v

  ;Shutdown
  inc BYTE [error]

  mov ax, 5307h
  mov bx, 01h
  mov cx, 03h
  int 15h
  jc .err

jmp .end 

.err:
  xor di, di
  mov ah, 09h
  mov al, BYTE [error]
  stosw

.end:
  cli
  hlt

  error db 0

  TIMES 505-($-__START__) db 0
  dw 0aa55h