.code16
.global _start
_start:
 cli
 xor %ax,%ax
 mov %ax,%ds
 mov %ax,%ss
 mov $0x7c00,%sp
 movl $0x48594452,0x508
 movl $0,0x500
 movw $0,0x504
loop:
 incl 0x500
 in $0x64,%al
 test $1,%al
 jz loop
 in $0x60,%al
 mov 0x504,%bx
 mov %al,0x600(%bx)
 inc %bx
 and $255,%bx
 mov %bx,0x504
 jmp loop
.org 510
.word 0xaa55