Subject: Re: Possible (but Evil) work-around for Pentium bug?
To: Michael K. Sanders <>
From: Don Lewis <>
List: current-users
Date: 11/13/1997 16:38:51
On Nov 12,  4:36pm, Rick Byers wrote:
} Subject: Re: Possible (but Evil) work-around for Pentium bug?
} I think the problem here is that we are confusing two issues.  There are
} TWO recently reported "pentium bugs".  The first (and probably the concern
} of people on this list), is the F00FC7C8 bug in Pentium and Pentium MMX
} chips which causes them to lock up.  This bug DOESN'T affect Pentium Pro
} or Pentium II chips.  The second bug is (although I don't know all the
} details), a "minor" floating point problem in Pentium II and Pentium Pros
} where a flag isn't being set when a floating point number doesn't convert
} to an integer properly (atleast, this is what I've read).
} According to Intel, only the Pentium Pro and Pentium IIs have software
} upgradable microcode.  This would explain the SCO fix - it fixes the
} floating point problem.

I don't know what the SCO fix does, but I don't think it fixes the flag
bug, either.  I saw this on BUGTRAQ (notice the statement in the last

--- Forwarded mail from Peter Bierman <bierman@APPLE.COM>

>From owner-bugtraq@NETSPACE.ORG Sat Nov  8 10:54:18 1997
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Date: 	Sat, 8 Nov 1997 05:08:36 -0800
Reply-To: Peter Bierman <bierman@APPLE.COM>
From: Peter Bierman <bierman@APPLE.COM>
Subject:      Re: Intel Pentium Bug

The following text is forwarded from the member mailing list of the
Undergraduate Projects Lab at the University of Wisconsin, Madison:

> On Fri, 7 Nov 1997, Chuck McKenzie wrote:
> <snip>
> > Intel recently acknowledged that they enabled the ability to update
> > microcode on Pentium chips several years ago. That's right folks, they put
> > a backdoor in your hardware. The good news is, it could be used to fix
> > this bug, should Intel be so inclined.
>       Think of the posibilitys... a nice little microcode virus...  I
> don't know how it works... could it be posible to nuke the microcode
> enough so that a computer wouldn't boot?

>From a Usenet post in intel.motherboards.pentium_pro:


The Pentium(R) Pro processor and Pentium(R) II Processor may contain
design defects or errors known as errata that may cause the product to
deviate from published specifications. Many times, the effects of the
errata can be avoided by implementing hardware or software
work-arounds, which are documented in the Pentium Pro Processor
Specification Update and the Pentium II Processor Specification Update.
Pentium Pro and Pentium II processors include a feature called
"reprogrammable microcode", which allows certain types of errata to be
worked around via microcode updates. The microcode updates reside in
the system BIOS and are loaded into the processor by the system BIOS
during the Power-On Self Test, or POST.

Intel provides microcode updates to system BIOS developers. System BIOS
code on motherboards based on Pentium Pro and Pentium II processors
contains microcode updates that are specific to silicon steppings of
the processor. Integrators must ensure the update matches the processor
stepping being used. When the system BIOS does not contain the
microcode update that matches the processor stepping, integrators must
install the latest update in the system BIOS before shipping the
system. Historically, systems based on the Pentium Pro and Pentium II
processors have been updated by upgrading the entire system BIOS with a
new revision of system BIOS that contains the correct microcode update.
However, such a process may be time consuming when assembling and
configuring many systems.

Intel has worked closely with BIOS developers to implement a processor
update Applications Programming Interface (API), which allows just the
microcode update within the system BIOS to be installed as needed.
Motherboards that contain a BIOS with the Intel-defined processor
update API can be quickly and easily updated with the processor update
utility, if required, without need for a complete system BIOS upgrade.
This utility is available to members of the IPD, GID and IPI programs

The latest revision of the PR440FX BIOS includes the latest microcode
update for the Pentium Pro processor. The flag erratum will not be
corrected by a microcode update.

Joe Goldmeer
Intel Internet Support

>I don't know if this applies to the Pentium and Pentium/MMX chips...

--    PGP at
"If you ask your children what they did today in school and they say
nothing.  We just want to remind you that nothing is really something."
-Ohio Education Association

--- End of forwarded message from Peter Bierman <bierman@APPLE.COM>