Please explain "386" vs. "686" versions
 

OK, a totally basic question.... What is the difference between "386" and "686" versions of kernels? I understand the difference between the 64 bit versions of kernels and kernels for other processors but I find that I can load either 386 or 686 versions on my PIII system and they work fine. Is there an advantage to using the 686 versions?

--- vino

Basically, the different kernel designations identify which instruction set the compiler was told to optimize for. An i686 CPU can run i586 and i386 instructions, so, as you observed, an i686 can run an i386 kernel. However, it may not execute as optimally as one specifically compiled for an i686.

These are the designations you will typically run into:

x86_64 Processors
* AMD's Athlon 64, Athlon 64-FX, and Opteron
* Intel EMT64 processors - Nocona Xeon, Pentium 4's using the E0 revision of the Prescott core (AKA Pentium 4, model F)

i686 Processors
* All Intel 32-bit Pentiums (excluding Pentium 1 and Pentium MMX)
* All AMD 32-bit Athlons

i586 Processors
* All 32-bit AMD Ks
* Pentium 1
* Pentium MMX

i386 Processors
* A generic "lowest common denominator" designation for Intel 80386 compatible CPUs (includes all of the above, but does not take advantage of extended instructions on those later CPUs).

Thanks Macemoneta. That clears things up.

One more question though: I've got a PIII system that I've installed the "386" version of a distro on. If I want to upgrade the kernel can I use the "686" version for the update or do I need to stick with "386" updates? Thanks for the info.

-- vino

Yes, you can use the i686 version of the kernel on a PIII. Normally, the appropriate kernel is selected automatically during installation, and via maintenance (apt, yum, up2date).

OK, thanks for the help.

-- vino