Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!know!samsung!xylogics!bu.edu!rpi!crdgw1!crdos1!davidsen
From: davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr)
Newsgroups: comp.arch
Subject: Re: Workstation Data Integrity
Keywords: interrupts
Message-ID: <2450@crdos1.crd.ge.COM>
Date: 24 Aug 90 19:45:37 GMT
References: <1990Aug3.204358.330@portia.Stanford.EDU> <40694@mips.mips.COM> <2399@crdos1.crd.ge.COM> <1990Aug10.171744.9639@zoo.toronto.edu> <14623@drilex.UUCP> <1990Aug20.151438.27121@ecn.purdue.edu> <10307@pt.cs.cmu.edu>
Reply-To: davidsen@crdos1.crd.ge.com (bill davidsen)
Organization: GE Corp R&D Center, Schenectady NY
Lines: 20

In article <10307@pt.cs.cmu.edu> lindsay@MATHOM.GANDALF.CS.CMU.EDU (Donald Lindsay) writes:

|                                                     Recall that the
| 8088 has prefix instructions, which change the addressing of the
| following instruction.  An NMI could be honored between the two, but
| the interrupt return would "forget" the prefixing.

  It could have been worse, it could have remembered it. Then when
servicing the interrupt the normal fetch from the CS:PC would have
fetched an instruction byte from somewhere else.

  I would think disallowing interrupts after prefix is the best way to
solve it, rather than try to hack things to save the state after the
chip was designed.

  Was this problem only with NMI? I've run a lot of interrupts into an
original XT and never seen a problem.
-- 
bill davidsen	(davidsen@crdos1.crd.GE.COM -or- uunet!crdgw1!crdos1!davidsen)
    VMS is a text-only adventure game. If you win you can use unix.