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-   -   Why does CentOS 5 claim to be i386 compatible when it's really not? (http://www.linux-archive.org/centos-development/464989-why-does-centos-5-claim-i386-compatible-when-its-really-not.html)

Akemi Yagi 12-13-2010 12:26 PM

Why does CentOS 5 claim to be i386 compatible when it's really not?
 
On Mon, Dec 13, 2010 at 5:18 AM, Martin Jungowski <martin@rhm.de> wrote:
> Another question just occurred to me: does this i686 limitation also
> apply to RHEL5?
>
> Thanks,
> Martin

As I wrote to you in the Forum thread[1], RHEL-4 and RHEL-5 provide no
support for i586.

Akemi / toracat

[1] http://www.centos.org/modules/newbb/viewtopic.php?topic_id=29278&forum=37
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Martin Jungowski 12-13-2010 12:47 PM

Why does CentOS 5 claim to be i386 compatible when it's really not?
 
On Mon, 13 Dec 2010 05:26:14 -0800 Akemi Yagi wrote:
> As I wrote to you in the Forum thread[1], RHEL-4 and RHEL-5 provide no
> support for i586.
>
> Akemi / toracat

Right, I forgot. Thanks again.

Martin

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Charlie Brady 12-14-2010 02:03 AM

Why does CentOS 5 claim to be i386 compatible when it's really not?
 
On Mon, 13 Dec 2010, Martin Jungowski wrote:

> It's not. It's just a general wondering as to why one would refer to
> something as i386 when in reality it's i686 instead.

You should ask Red Hat. You're wasting your time (and ours) asking here.
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Ross Walker 12-14-2010 05:14 PM

Why does CentOS 5 claim to be i386 compatible when it's really not?
 
On Mon, Dec 13, 2010 at 5:02 AM, Martin Jungowski <martin@rhm.de> wrote:
> On Sun, 12 Dec 2010 17:08:24 -0500 Peter A wrote:
>> Over the past few years, i386 has become a synonym for 32bit rather than
>> "it will run on a 80386". The RPM package for the kernel is correctly
>> labeled as i686, its just the name of the distro that remained i386.
>
> That's why I'm asking whether or not it would make more sense to rename
> the distro to i686 instead. It might make perfect sense in a very
> colloquial way but from a technical point of view i386 suggests 32-bit
> 80386 compatibility. Either way, it's just a suggestion and general
> wondering since I wasn't aware of what i386 had become in the US.

It actually makes more sense to call the distro x86, better to peg it
to a particular architecture then a CPU release.

Then one has x86 (32-bit) and x86_64 (64-bit).

But this is all decided by Redhat, CentOS is just a RHEL recompilation
with the intellectual property stripped out.

-Ross
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Jeff Johnson 12-14-2010 05:29 PM

Why does CentOS 5 claim to be i386 compatible when it's really not?
 
On Dec 14, 2010, at 1:14 PM, Ross Walker wrote:
>
> It actually makes more sense to call the distro x86, better to peg it
> to a particular architecture then a CPU release.
>
> Then one has x86 (32-bit) and x86_64 (64-bit).
>

Sure there's an appealing symmetry with "x86" <-> "x86_64".
The problem is that the names keep changing for marketing
and technical reasons. Even "i686" and "i586" are mostly
meaningless jargon. E.g. the linux kernel chose to start
returning "i686" as a generic, not specific, and rely
on precise details in /proc/cpuinfo years and years ago.

> But this is all decided by Redhat, CentOS is just a RHEL recompilation
> with the intellectual property stripped out.
>

Nothing decided by RedHat (or Intel) prevents using "ia32e"
or "i786" as a cpu architecture identifier in CentOS.

It's a "Principle of Least Surprise" wrto users that continues to use "i386"
as an identifier.

73 de Jeff

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Martin Jungowski 12-15-2010 09:33 AM

Why does CentOS 5 claim to be i386 compatible when it's really not?
 
On Tue, 14 Dec 2010 13:29:29 -0500 Jeff Johnson wrote:
> Sure there's an appealing symmetry with "x86" <-> "x86_64". The problem
> is that the names keep changing for marketing and technical reasons.
> Even "i686" and "i586" are mostly meaningless jargon. E.g. the linux
> kernel chose to start returning "i686" as a generic, not specific, and
> rely on precise details in /proc/cpuinfo years and years ago.

This could be because ever since the 1995 introduction of the i686
architecture with the Pentium Pro the core architecture hasn't changed
significantly. AMD's K7 is fully i686 compatible, the K8 is a K7 core
plus 64-bit features, and the K10 is an improved K8. At it's very core
(in terms of instruction set, not in terms of actual silicon
implementation) even the latest Phenom II X6 is still a fully i686
compatible K7. Intel tried a new architecture with the Pentium 4 but
failed spectacularly as we all know, and returned to an improvied i686
processor with its Pentium M (aka Banias), Core and Core 2 series. The
Core i7 is just like the Phenom II - a full i686 instruction set with 64-
bit features.

Martin

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Timo Schoeler 12-15-2010 10:30 AM

Why does CentOS 5 claim to be i386 compatible when it's really not?
 
thus Martin Jungowski spake:
> On Tue, 14 Dec 2010 13:29:29 -0500 Jeff Johnson wrote:
>> Sure there's an appealing symmetry with "x86" <-> "x86_64". The problem
>> is that the names keep changing for marketing and technical reasons.
>> Even "i686" and "i586" are mostly meaningless jargon. E.g. the linux
>> kernel chose to start returning "i686" as a generic, not specific, and
>> rely on precise details in /proc/cpuinfo years and years ago.
>
> This could be because ever since the 1995 introduction of the i686
> architecture with the Pentium Pro the core architecture hasn't changed
> significantly. AMD's K7 is fully i686 compatible, the K8 is a K7 core
> plus 64-bit features, and the K10 is an improved K8. At it's very core
> (in terms of instruction set, not in terms of actual silicon
> implementation) even the latest Phenom II X6 is still a fully i686
> compatible K7. Intel tried a new architecture with the Pentium 4 but
> failed spectacularly as we all know, and returned to an improvied i686
> processor with its Pentium M (aka Banias), Core and Core 2 series. The
> Core i7 is just like the Phenom II - a full i686 instruction set with 64-
> bit features.

The P6 design in the Pentium Pro was the next big leap after the i386
featured an MMU -- it was the first x86 CPU to feature out of order
execution, and it was one of the first x86 CPUs to 'emulate' x86; for
doing this, it used an internal RISC-based design (AFAIR the NexGen
Nx586 was the first x86 CPU to do this, and it features speculative
execution, as well). Mind the extreme 16bit performance problem the
Pentium Pro had.

> Martin

Timo
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Alan Bartlett 12-15-2010 03:54 PM

Why does CentOS 5 claim to be i386 compatible when it's really not?
 
All,

As interesting (or not) as this discussion may be, please note that
this is the CentOS-devel mailing list and, thus, is not the
appropriate venue -- as it has no relevance to the ongoing development
of CentOS.

Putting that into perspective, the core components of the CentOS
Project are those products that are aimed to be 100% binary compatible
with the Upstream Vendor's products. Therefore if i386 is used
upstream as a label, it will also be used likewise by the CentOS
Project.

Please take the discussion of processors, instruction sets, et al, to
the CentOS general m/l.

In peace and friendship,
Alan. :-)
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