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From: Robert Heller <heller@deepsoft.com>
Subject: Re: what do i386 and i686 refer to?
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>> 
Date: Mon, 26 May 2003 23:55:59 +0000

  Jim Kroger <jimkkREMOVE@THISumich.edu.invalid>,
  In a message on Mon, 26 May 2003 18:55:29 -0400, wrote :

JK> Nobody has yet said what i386 and i686 refer to.
JK> 
JK> Is it the cpu?  What is an architecture?

CPUs are defined by their architecture.  The architecture defines things
like the instruction set and so on.

i386 means any processor that is based on the 80386 processor, which is
the first true 32-bit processor of the x86 family, which started with
the 8086 and 8088 (the processor in the first IBM-PC), and then moved up
to the 80286 (in the IBM PS/2 and PC/AT boxes). And then to the 80386.

i486 refers to the 80486, which is a 'marriage' of an 80386 and 80387
(FPU), with some other enhancements (double and quad clocking, on chip
cache, etc.).

i586 refers to the 80586 (aka Pentium), a more advanced version.

i686 refers to the 80686 (aka PII, PIII, and P4), still more advanced.

Most of the time, if you have an x86 machine (typical 'IBM-PC' type
machine), you want the i386 binaries.  i486 RPMs are rare and don't
have much advantage over i386.  i586 only make sense on true Pentiums
and are actually *worse* then i386 on PII and up (it has to do with
instruction scheduling weirdnesses on the old Pentiums).

There are only a few places where optimizing beyond the i386 is sensible
-- typically the kernel itself and glibc.

Sometimes you will see 'noarch' as the RPM's architecture -- this means
that the RPM contains no actual binary code.  Instead the RPM contains
processor independent data files (such as extra data for GIMP or an
empty database tree for a database or fonts for ghostscript or X11).

'src' as the architecture means that the RPM contains only source code,
and needs to be (re-)built to be installed (to be useful).

OH, there are RPMs for other sorts of CPUs, like .ppc.rpm -- these are
PowerPC RPMs (for Macintosh's running Linux) or .s390.rpm for IBM
System/390 processors (IBM big mainframe systems) or .sparc.rpm for SUN
Microsystems's Sparc processors, etc.

JK>  
JK> Thanks 
JK> Jim 
JK>  
JK> --  
JK> A list of jazz guitar instruction websites: 
JK> www-personal.umich.edu/~jimkk/jazzfast.html
JK>  
JK> rseegmoarjk 
JK>  
JK>                                          






                                         

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