Re: Why are there only i686 and i586 Version of glibc and kernel? -- i386 is still around

[Per Bjornsson <perbj stanford edu>]

Matthew Miller wrote:

> As I've said elsewhere, I think this niche would be better served by a
> Fedora Lite distribution than by making Fedora Core do it. (In fact, I'd
> include i586 with that.)

And as others have said before, there are still plenty of K6 and other 
processors still around (586-instruction-set-compatible, but not fully 
686) that are admittedly far from the front line of computing but which 
are still used in desktop-style situations. (I of course have personal 
reasons to want to save this class: My girlfriend has a laptop with a 
K6; admittedly it's seeing a lot less use since I bought a new laptop 
but it's still nice to have around. I'm planning to put FC2 on it within 
days, it's our only computer that is still running FC1.) Dumping these 
without a really good reason would IMHO be a shame. (There's also the 
class of low-power Via platforms; only the pretty recent C3's have full 
CMOV and thus older ones don't work with gcc's 686 code. These are also 
fairly recent and don't IMHO deserve to be tossed on the "unsupported" 
dumping ground just yet.)

Going to i486 as the minimum,as opposed to sticking with 386, seems very 
rational, considering Jakub Jelinek's investigations of the feasibility 
of using NPTL on i386 (apparently a semi-functional hack essentially, 
which would suck up maintenance resources for minimal gain - and zero 
gain for any Fedora- or Red Hat-supported configuration) and i486 (it's 
got the stuff needed to do it sanely) it seems that choosing i486 as a 
baseline for now has the best pain-to-gain ratio for the time being, 
especially given the comments heard recently on this mailing list that 
the 586 really didn't bring much particularly useful to the table in 
terms of instructions that really speed things up. [Note that the 
comments on NPTL are meant to essentially be paraphrasing what Jakub 
Jelinek has said on the subject, I have no sufficient knowledge to add 
anything on that front - and if I misunderstood that's all my fault.]

Since this would effectively actually _lower_ the bar for using Fedora 
with marginal modifications (essentially recompile the kernel for i486, 
as opposed to rpm being broken since it wants to link with NPTL that 
doesn't currently exist in <586 packages) it should even make a lot of 
people experimenting with low-end systems happy. Even though it's not a 
supported feature of Fedora Core, preventing it for minimal gain sounds 
useless to me.

Of course, at some point it's likely going to make sense to move to 
i686+CMOV (gcc's 686 definition as far as I understand) as a base level, 
which is essentially the next sensible higher option available. I 
absolutely do not think that the time is here yet.

/Per

--
Per Bjornsson <perbj at stanford dot edu>
Ph.D. Candidate, Department of Applied Physics, Stanford University