[comp.arch] 80268 bugs

koopman@a.gp.cs.cmu.edu (Philip Koopman) (08/05/89)

There are more hardware bugs in the 80286 than just the
interrupt problem that's being discussed.  The one that
has bitten me is that:

  PUSH AX
  PUSH BX
  RET (long)

doesn't work (it used to work on the 8088!)

But, 
  PUSH AX
  PUSH BX
  NOP
  RET (long)

does work.  Probably, this has to do with pipelining used
to make the PUSH instruction very fast.
I know this sounds like a weird thing to be doing on a '286,
but efficient Forth systems have some unusual requirements.

  Phil Koopman                koopman@greyhound.ece.cmu.edu   Arpanet
  2525A Wexford Run Rd.
  Wexford, PA  15090
Senior Scientist at Harris Semiconductor.
I don't speak for them, and they don't speak for me.

mccaugh@s.cs.uiuc.edu (08/09/89)

 Thank you for this warning. Now my question is: where is all this documented?
 Can I obtain a '286-code manual that I can trust?