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compiler optimizing

From: Christopher Browne <cbbrowne@acm.org>
Subject: Re: what do i386 and i686 refer to?
Date: 27  01:52:38 GMT
References: <jimkkREMOVE-A7C786.12522526052003@visonmassif.rs.itd.umich.edu>
<pan.2003.05.26.17.21.12.321709@bd-home-comp.no-ip.org>
<slrnbd4pjo.ilg.mattdm@jadzia.bu.edu>
<jimkkREMOVE-54252C.18552926052003@visonmassif.rs.itd.umich.edu> 

After a long battle with technology,Jim Kroger <jimkkREMOVE@THISumich.edu.invalid>, an earthling, wrote:
> Nobody has yet said what i386 and i686 refer to.
>
> Is it the cpu?  What is an architecture?

"i386" refers to the architecture ("design") of the Intel ("i" is for
"Intel") 80386 processor.

The 80386 was the first kind of processor on which Linux was made to
run.

"i686" refers to a later series, again from Intel, of processors with
additional capabilities and instructions.  Intel decided by that point
not to number them as "80686", due to inability to put trademarks on
numbers.  "i686" points to the Pentium Pro and Pentium II chips, which
notably added in MMX instructions.

The notion of "architecture" is related to that of "design;" these
"architectures" involve computer CPUs with particular sets of
capabilities.  When someone "architects" a building, that involves
designing in building features to fit with purposes planned for the
building, as well as engaging in actvities fitting with the design of
the building.

The designers of computer processors generally build a variety of
related CPUs; the "architecture" addresses things like:
 - the way registers are set up; these are "memory cells" on the
   chip that are used to store addresses or values that are to be
   processed; 
 - the model by which memory will be addressed;
 - the set of instructions used to control the CPU.

Intel produced "80386" processors with varying sets of features; the
"architecture" characterizes the similarities between those
processors.

Later designs from Intel have generally been derivative of the earlier
ones.  Code written for "80386" chips generally runs quite well on
later models, and, indeed, on later architectures such as i486, i586,
and i686.  The later series' offer additional capabilities, but it is
not always mandatory to make use of all the "new stuff."
-- 
"cbbrowne","@","ntlug.org"
http://www3.sympatico.ca/cbbrowne/sgml.html
"you  can   obvioulsy understand what  i'm  saying.  you're just being
pendantic." -- bazzz777@yahoo.com

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