Leonard den Ottolander wrote:
This issue was discussed in the thread "Making NPTL the default for FC3, vanilla i386 support". Both i386s and i486s are already no longer supported since FC 1. Try running rpm on either of these CPUs and see it fail. See https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=103078 .
FYI, the original Cyrix 686 (M1?) was only i486 compatible. You had to go with the 686"L" or M2 to get full i586 ISA compatibility.
Frankly, I don't think people recognize the _real_ reason for trying to keep i386/486 ISA compatibility. It's not to support old systems, but to support i386/486 ISA embedded microprocessor cores in all sorts of black box solutions. These solutions have full desktops/GUIs far more than you may think.
All it takes is one major black box vendors to adopt Fedora and we're talking over a 1% marketshare.
GCC still pumps out i386 ISA code, while making other optimizations. So anything that has a patch or otherwise that breaks this should be revisited. So there is still a good reason to strive for i386/486 ISA.
So if there is the intention of making the move to i486 as the minimum arch we could just as well make the jump to i586.
I would continue to favor i386 with i686 (Pentium Pro) optimizations.
i586 (Pentium) causes a lot of de-optimizations in newer processors, even Intel's own. Why? Understand that about 80% of "Pentium optimizations" were really "errata workarounds." The Pentium was the first superscalar x86 design, and boy did it have some real muck-ups that had to be compensated in software (like the ALU LOAD being 3x slower, which id found it far faster to load via integers via the FPU instead).