uname

[James Wilkinson]

Kaushal Shriyan wrote:
> >On Thu, Jul 27, 2006 at 04:26:12PM +0530, Kaushal Shriyan wrote:
> I have a query on uname
> 1)uname -i prints i386
> 2)uname -m prints i686

Matthew Miller replied:
>      -m, --machine
>             print the machine hardware name
>
>      -p, --processor
>             print the processor type
>
>      -i, --hardware-platform
>             print the hardware platform

Kaushal replied:
> I know this using man uname
> My query is what is "the machine hardware" name and what is "the
> hardware platform

Try this, then. An i486 was basically compatible with an i386. So is a
Celeron, Athlon XP, or Core Duo (when running in 32 bit mode). Apart
from a few new instructions on newer chips (which don't get used that
much), they all run the same software [1].

>From Linux's point of view, a 286 was radically different -- it didn't
*have* a 32 bit mode (or several other things).

A "hardware platform", as uname calls it, is simply the family of
computers that can run the same software. There just wasn't a good name
for the "normal 32-bit Intel compatible family as found in modern PCs"
until about six years ago, when Intel came up with the name "IA32". The
alternative "x86" also applied to 8086s and 286s, which aren't 32 bit
and aren't good enough for Linux [2].

So uname used "i386" to mean "everything compatible with a 386" and
"software suitable for running on a 386 in 32 bit mode".

The other two options Matthew mentioned talk about your particular
machine, and the compatibility level of the processor in it. Calling it
an i686 means that it has all the instructions the Pentium Pro had and
can run everything the Pentium Pro could. (If Intel hadn't switched
naming schemes, the Pentium Pro would have been the Intel i686.)

Hope this helps,

James.

[1] Assuming that the i386 and i486 had FPUs...
[2] Ignoring ELKS for the purpose of this email.
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