BITS 16
CPU 8086

diskpointer equ 0x1e*4
dbtbase equ 0x100

_start:
    jmp main

main:
    push ds
    mov si, diskpointer
    lds si, [si]
    mov di, dbtbase
    mov cx, 0x0a
    cld
    rep movsb
    pop ds
    mov al, 9  ; sectors per track
    mov di, dbtbase
    mov [di+4], al
    mov di, diskpointer
    mov [di], word dbtbase
    mov [di+2], ds
    retf