xor bx, bx
call read_sector
; check is the VBR bootable (ends with 0x55 0xaa), if not halt
cmp word [0x7dfe], 0xaa55
jne .not_bootable
mov dl, [BOOT_DRIVE]
xor bx, bx
call read_sector
; check is the VBR bootable (ends with 0x55 0xaa), if not halt
cmp word [0x7dfe], 0xaa55
jne .not_bootable
mov dl, [BOOT_DRIVE]