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From: dhinds@portia.Stanford.EDU (David Hinds)
Newsgroups: comp.sys.intel
Subject: Re: 80386DX-33 SX211
Message-ID: <1990Jul4.174608.23646@portia.Stanford.EDU>
Date: 4 Jul 90 17:46:08 GMT
References: <1990Jul4.084846.7262@pilikia.pegasus.com>
Distribution: usa
Organization: AIR, Stanford University
Lines: 28

In article <1990Jul4.084846.7262@pilikia.pegasus.com> art@pilikia.pegasus.com (Art Neilson) writes:
>
>I recently learned of a bug in the 80386DX processor version SX211.
>The latest release of ISC UNIX 2.2 enables instruction pipelining,
>causing my system to hang during installation of this new release.
>I tried putting my drive and controller in another 386 box with a
>different CPU, the OS installed fine.  I put the drive and controller
>back in my system and tried booting the system.  The kernel panics
>and dumps everytime it loads.  Can anyone confirm the pipeline bug
>in the 80386DX processor version SX211 and explain just what instruction
>pipelining is ? ...

    This sounds very unreasonable to me.  Instruction pipelining refers
to overlapping the execution of several instructions as they pass through
different functional units of the chip.  So, for example, while one
instruction is being fetched, another is being decoded, and another is
being executed.  This is an intrinsic feature of the 80386 - it is not
something that can be switched on and off by an operating system.  The
80386 also has an "address pipelining" mode which allows some overlap
of memory accesses.  This mode is affected by the sort of memory system
attached to the CPU, but is also not subject to software control.
    It seems much more likely that there is some other incompatibility
responsible for the failure of your Unix to load.  It isn't inconceivable
that there is a bug in the 386DX, but I haven't heard of any, and it
could not be as you describe.

 -David Hinds
  dhinds@popserver.stanford.edu