Path: myrddin.imat.com!miwok!news.scruz.net!kithrup.com!news.Stanford.EDU!agate!howland.erols.net!cs.utexas.edu!geraldo.cc.utexas.edu!not-for-mail From: noname@noname.com Newsgroups: comp.os.linux.advocacy Subject: This code will lock up any P5 machine, even usermode Linux! (F0 0F C7 C8) Date: Thu, 06 Nov 1997 21:57:33 -0800 Organization: The University of Texas at Austin, Austin, Texas Lines: 7 Message-ID: <3462ADCD.135B@noname.com> NNTP-Posting-Host: dial-102-5.ots.utexas.edu Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0 (Win95; I) Hi, Check this out. If you execute F0 0F C7 C8 on a P5 it will lock the machine up. This is true for any operating system including usermode Linux. It's pretty cool. Basically, the opcodes are an invalid form of cmpxchg8b eax with a lock prefix. Has anyone seen this before? The problem doesn't show itself for the Pentium Pro or Pentium 2.