[CentOS-devel] Why does CentOS 5 claim to be i386 compatible when it's really not?

Martin Jungowski

martin at rhm.de
Wed Dec 15 10:33:23 UTC 2010

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.


Rieke Computersysteme GmbH
Hellerholz 5
D-82061 Neuried
Email: martin[at]rhm[dot]de

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