On Mon, 11 Dec 2006, James Wilkinson wrote:
Les wrote:
I don't know what you are working on Mike, but if it helps, I installed
to a 433Mhz celeron with the i386 package and when I ran that command I
got:
kernel-2.6.18-1.2798.fc6.i586
kernel-2.6.18-1.2849.fc6.i586
kernel-devel-2.6.18-1.2798.fc6.i586
kernel-devel-2.6.18-1.2849.fc6.i586
kernel-headers-2.6.18-1.2849.fc6.i386
I was sort of expecting them all to say i386??? Maybe someone can help
us understand what's happening.
i586 will work, but an i686 kernel will work slightly better on a
Celeron.
The basic 32 bit set of instructions that x86 Linux uses were introduced
with the Intel i386 back in 1986. Later Intel processors added extra
instructions to help in specific cases. (Later on, various "multimedia"
instructions were also added, but that's a separate discussion.)
Most user-space programs don't actually need or gain from those extra
instructions. So Fedora compiles most programs using only i386
instructions -- hence the "i386" in most package names.
Some packages (the kernel and glibc, for example) *can* make use of the
extra instructions. So Fedora provides an i686 version of those
packages, which do use the extra instructions. Unfortunately, there are
still some processors which don't support the i686 level of instructions
(Via only recently started supporting them, and AMD K6s are still used).
For these processors, Fedora provides an i586 version. (i586
instructions are still better than just the i386 instruction set in
these cases).
i586 programs will work on later processors, but i586 processors don't
know how to handle i686 instructions. (If they did, they'd be i686
processors).
I'm not sure whether the kernel headers actually contain *any*
instructions -- if they do, they'd be tiny portions of assembler. They
don't use processor-specific instructions, so count as i386.
Hope this helps,
IIRC, the i586 was peculiar to original Pentium and Pentium MMS. I recall
some discussion that optimal instruction ordering was different enough on
i586 and i686 that running i586 kernels on i686 chips would result in more
or less significant performance issues.
James.
--
Matthew Saltzman
Clemson University Math Sciences
mjs AT clemson DOT edu
http://www.math.clemson.edu/~mjs
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