ray@philmtl.philips.ca (Raymond Dunn) (05/19/89)
Go into DEBUG and enter and *trace* through the following instructions with
DEBUG on an 80286 or 80386 based system:
MOV BX,FFFF
MOV AL,[BX]
In trying to display the data contents DEBUG accesses a *word* and causes a
segment overflow trap which hangs the machine!
--
Ray Dunn. | UUCP: ..!uunet!philmtl!ray
Philips Electronics Ltd. | TEL : (514) 744-8200 Ext: 2347
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St Laurent. Quebec. H4M 2S9 | TLX : 05-824090msschaa@cs.vu.nl (Schaap MS) (05/25/89)
In article <514@philmtl.philips.ca> ray@philmtl.UUCP (Raymond Dunn) writes: >Go into DEBUG and enter and *trace* through the following instructions with >DEBUG on an 80286 or 80386 based system: > > MOV BX,FFFF > MOV AL,[BX] > >In trying to display the data contents DEBUG accesses a *word* and causes a >segment overflow trap which hangs the machine! > I don't know if it works, but it's worth a try. Try MOV BX,FFFF MOV AL, BYTE PTR [BX] Michael
afscian@violet.waterloo.edu (Anthony Scian) (05/26/89)
In article <2611@solo3.cs.vu.nl> msschaa@cs.vu.nl (Schaap MS) writes: >>Go into DEBUG and enter and *trace* through the following instructions with >>DEBUG on an 80286 or 80386 based system: >> >> MOV BX,FFFF >> MOV AL,[BX] >> >>In trying to display the data contents DEBUG accesses a *word* and causes a >>segment overflow trap which hangs the machine! You can thank Microsoft for this behaviour because they used Intel reserved interrupts for their own purposes (MS-DOS). Any interrupt under 20h is reserved by Intel for future architectural enhancement. I think the interrupt that occurs in this case is a disk I/O BIOS (I don't have an Intel manual here so I could be wrong). Anthony //// Anthony Scian afscian@violet.uwaterloo.ca afscian@violet.waterloo.edu //// "I can't believe the news today, I can't close my eyes and make it go away" -U2
rde@ukc.ac.uk (R.D.Eager) (05/27/89)
In article <14109@watdragon.waterloo.edu> afscian@violet.waterloo.edu (Anthony Scian) writes: >You can thank Microsoft for this behaviour because they used Intel ^^^^^^^^^ IBM, surely? For using the interrupts for the BIOS? and for devices? MS-DOS interrupts start at 20H..... -- Bob Eager rde@ukc.UUCP ...!mcvax!ukc!rde Phone: +44 227 764000 ext 7589
alpope@token.Sun.COM (Alan Pope) (05/31/89)
In article <14109@watdragon.waterloo.edu>, afscian@violet.waterloo.edu (Anthony Scian) writes: > In article <2611@solo3.cs.vu.nl> msschaa@cs.vu.nl (Schaap MS) writes: > >>Go into DEBUG and enter and *trace* through the following instructions with > >>DEBUG on an 80286 or 80386 based system: > >> > >> MOV BX,FFFF > >> MOV AL,[BX] > >> > >>In trying to display the data contents DEBUG accesses a *word* and causes a > >>segment overflow trap which hangs the machine! > You can thank Microsoft for this behaviour because they used Intel > reserved interrupts for their own purposes (MS-DOS). > [stuff deleted] > Anthony > //// Anthony Scian afscian@violet.uwaterloo.ca afscian@violet.waterloo.edu //// IBM used the reserved interrupts, not Microsoft. Keep your facts straight. Alan L. Pope alpope@sun.com