UNIX for Advanced & Expert Users

[jack@localhost 1]$ cat boot.S
.code16
#define SETUPLEN  4
#define BOOTSEG  0x7C0
#define INITSEG  0x900

.text
a:
mov $BOOTSEG, %ax
mov %ax, %ds
mov $INITSEG, %ax
mov %ax, %es
mov $256, %cx
sub %si, %si
sub %di, %di
rep
movsw

jmp 0x9000+go-a

go:
mov %cs, %ax
mov %ax, %ds
mov %ax, %es
mov %ax, %ss
mov $0xFF00, %sp

load_setup:
mov $0x0000, %dx
mov $0x0002, %cx
mov $0x0200, %bx
mov $0x0200+SETUPLEN, %ax
int $0x13                           //timeout happens here
jnc ok_load_setup
mov $0x0000,%dx
mov $0x0000,%ax
int $0x13
jmp load_setup

ok_load_setup:
mov $0x00, %dl
mov $0x0800, %ax
int $0x13
mov $0x00, %ch
mov %cx, %cs 
mov $INITSEG, %ax
mov %ax, %es

mov $0x03, %ah
xor %bh, %bh
int $0x10

mov $24, %cx
mov $0x0007, %bx
mov msg, %bp
mov $0x1301, %ax
int $0x10

msg:
.byte 13, 10


.org 510
.word 0xaa55