From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: ** X-Spam-Status: No, score=2.2 required=5.0 tests=BAYES_00,FROM_WORDY, REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,63e8a95e8331225 X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-04-21 18:41:00 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!feed2.news.rcn.net!feed1.news.rcn.net!rcn!not-for-mail From: "Frank J. Lhota" Newsgroups: comp.lang.ada Subject: Re: Partial Hardware Protection for Buffer Overrun Exploits Date: Mon, 21 Apr 2003 21:40:49 -0400 Message-ID: References: <3EA41F8E.8030305@cogeco.ca> Reply-To: "Frank J. Lhota" X-Trace: UmFuZG9tSVbQaxqqgyEhYIyWBymPjuJ4uptAHriAQv7JArVyuCBiguYOIqk7TtLh X-Complaints-To: abuse@rcn.com NNTP-Posting-Date: 22 Apr 2003 01:40:33 GMT X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Priority: 3 X-Newsreader: Microsoft Outlook Express 6.00.2800.1106 X-MSMail-Priority: Normal Xref: archiver1.google.com comp.lang.ada:36342 Date: 2003-04-22T01:40:33+00:00 List-Id: wrote in message news:qRVoa.554917$3D1.304762@sccrnsc01... > When Intel came out with Protected Mode Bill Gates declared it "brain > dead" and they came up with the "solution" of doing a restart of the CPU > to shake off the shackles of protection. The first Intel chips that supported protected mode were the rarely-used 80186 and the 80286 chips that powered the IBM PC/AT. These early chips supported a command for transitioning from real to protected mode, but no simple command for transitioning back to real mode. This is what earned these chips the "brain dead" assessment from Gates. The lack of a quick way to get back to real mode was a problem for MS, who wanted protected-mode extensions to DOS (such as Windows 3.x and OS/2 1.x) to be able to use the real mode I/O kernel of DOS. Their solution was the "mini-reboot" of the CPU, for which they paid a performance penalty. All of these problems went away with the next generation of Intel chips (the 80386 and beyond), which can quickly toggle between real and protected modes.