explain div weirdness

1 year ago · 1bad40143e
parent 108040ae01
commit 1bad40143e
1 changed files with 1 additions and 1 deletions
--- a/boot0.s
+++ b/boot0.s
@ -59,7 +59,7 @@ bits 16
  setne cl   ; sector - 1 = LBA % (sectors per track)
  inc cl
  xor ah, ah ; zero-extend temp
-  xor dx, dx ; TODO: explain why this is needed for div
+  xor dx, dx ; div by 16-bit register divides dx:ax, so we zero dx
  div bx     ; ah = mod (head), al = div (cylinder)
  mov dh, ah ; head