.code16
_start:
    /* Normalize CS + other selectors */
    ljmp $0x00,$1f
1:  xor %ax, %ax
    mov %ax, %ds
    mov %ax, %ss
    mov %ax, %es
    mov %ax, %gs
    mov %ax, %fs
2:  cli
    hlt
    jmp 2b

    .org 510
    .byte 0x55
    .byte 0xAA