OSDev

  mov ax,1+fixed_fats*fixed_fatsize
  mov cx,fixed_rootsize
@@:
  push ax
  push cx
  push dx

  push ds
  pop es
  mov bx,7E00h
  mov cl,fixed_spt

  and dx,7Fh ; можно вынести за пределы цикла

  div cl
  mov ch,al
  mov cl,ah
  shr ch,1
  adc dh,dh
  inc cx
  mov ax,201h
  int 13h
  jc short error

  stdcall putstr,[$$-2],[7FFEh]
  db 13,10,"Root sector/Last entry:",32,128,"/",128,0

  pop dx
  pop cx
  pop ax
  inc ax
  loop @b