On 12/11/06, Matthew Saltzman mjs@ces.clemson.edu wrote:
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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Is everything right with my system now that it says i686 instead of i586?
Kind Regards, Mike