From: "H. Peter Anvin" <hpa@zytor.com>
To: Arjan van de Ven <arjan@linux.intel.com>
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>,
Thomas Gleixner <tglx@linutronix.de>, jamal <hadi@cyberus.ca>,
Suresh Siddha <suresh.b.siddha@intel.com>,
Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
Jan Beulich <jbeulich@novell.com>
Subject: Re: i387/FPU init issues...
Date: Sun, 04 May 2008 14:07:24 -0700 [thread overview]
Message-ID: <481E258C.20003@zytor.com> (raw)
In-Reply-To: <481E1B89.8020708@linux.intel.com>
Arjan van de Ven wrote:
>>
>> It has retroactively been added to the documented list for all P6 core
>> chips - that should mean it works on all of them. The most common
>> reason for not documenting something (other than various Pure Evil NDA
>> schemes) is that it hasn't been properly verified. However,
>> verification can be done a posteori.
>
> the other reason is that certain groups of "unknown" opcodes will act as
> NOP.
> Which for this purpose is .. exactly the right thing retroactive
>
Specifically, I believe the P6 added a whole class of instructions which
would act as NOP's if used on older chips. It has been used for
prefetch instructions, etc. At some point, the 0F 1F /0 group was
declared to be NOP, and nothing else, for all future.
-hpa
prev parent reply other threads:[~2008-05-04 21:11 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-03 10:32 i387/FPU init issues jamal
2008-05-03 10:57 ` James Courtier-Dutton
2008-05-03 13:53 ` jamal
2008-05-03 15:31 ` Thomas Gleixner
2008-05-03 17:02 ` jamal
2008-05-03 17:34 ` Ingo Molnar
2008-05-03 17:39 ` Thomas Gleixner
2008-05-04 21:31 ` Jan Engelhardt
2008-05-04 21:37 ` H. Peter Anvin
2008-05-05 13:00 ` Lennart Sorensen
2008-05-03 18:48 ` H. Peter Anvin
2008-05-03 20:07 ` Mikael Pettersson
2008-05-03 20:03 ` H. Peter Anvin
2008-05-03 17:42 ` H. Peter Anvin
2008-05-03 17:50 ` James Courtier-Dutton
2008-05-03 17:51 ` H. Peter Anvin
2008-05-03 18:18 ` Thomas Gleixner
2008-05-03 18:58 ` Mikael Pettersson
2008-05-03 19:03 ` H. Peter Anvin
2008-05-03 19:08 ` H. Peter Anvin
2008-05-03 19:17 ` Thomas Gleixner
2008-05-03 19:24 ` H. Peter Anvin
2008-05-03 19:54 ` Ingo Molnar
2008-05-03 19:56 ` H. Peter Anvin
2008-05-03 19:49 ` Maciej W. Rozycki
2008-05-03 20:06 ` H. Peter Anvin
2008-05-03 21:17 ` Maciej W. Rozycki
2008-05-03 21:46 ` jamal
[not found] ` <Pine.LNX.4.55.0805032209480.20206@c <1209851170.6972.64.camel@localhost>
2008-05-04 13:08 ` Sebastian Herbszt
2008-05-04 15:06 ` jamal
2008-05-04 15:21 ` Sebastian Herbszt
2008-05-04 20:24 ` Arjan van de Ven
2008-05-04 21:07 ` H. Peter Anvin [this message]
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