[sf-lug] Perhaps Grimm news of Linux dropping i486 support?

aaronco36 at sdf.org aaronco36 at sdf.org
Fri Nov 4 11:18:07 PDT 2022

News of potentially dropping i486 support.

Quoting Linus Torvalds <torvalds at linux-foundation.org> from [01]:
Maybe we should just bite the bullet, and say that we only support
x86-32 with 'cmpxchg8b' (ie Pentium and later).

Get rid of all the "emulate 64-bit atomics with cli/sti, knowing that
nobody has SMP on those CPU's anyway", and implement a generic x86-32
xchg() setup using that try_cmpxchg64 loop.

I think most (all?) distros already enable X86_PAE anyway, which makes
that X86_CMPXCHG64 be part of the base requirement.

Not that I'm convinced most distros even do 32-bit development anyway
these days.

(Of course, if we require X86_CMPXCHG64, we'll also hit some of the
odd clone CPU's that actually *do* support the instruction, but do not
report it in cpuid due to an odd old Windows NT bug. IOW, things like
the Cyrix and Transmeta CPU's did support the instruction, but had the
CX8 bit clear because otherwise NT wouldn't boot. We may or may not
get those cases right, but I doubt anybody really has any of those old

We got rid of i386 support back in 2012. Maybe it's time to get rid of
i486 support in 2022?

That way we could finally get rid of CONFIG_MATH_EMULATION too.

Here are a pair of current ideas, among others, for running a quaint
selection of remaining 32bit Linux distros as Oracle Virtualbox guests
until such time as development for 32bit Linux distros (including the
i686-specific architecture) might cease:

Network domain name 'grimmbros'....
1. amd64 virtualbox host OS 'snow7dwarves'
Debian-based 32bit guest machines....

a. VBox-label and guestname 'sleepy' for BunsenLabs Linux [02]
b.     "             "      'bashful' for CrunchBang++ Linux [03]
d.     "             "      'grumpy' for Debian GNU/Linux Stable
'Bullseye' [04]
e.     "             "      'happy' for Devuan GNU+Linux Chimaera
(systemD-free based on Bullseye) [05]
f.     "             "      'docdwrf' for Debian GNU/Linux Testing
'Bookworm' [06]
g.     "             "      'sneezy' for Devuan GNU+Linux Daedalus
(systemD-free based on Bookworm) [07]
h.     "             "      'dopey' for antiX Linux [08]
i.     "             "      'evilqueen for MX Linux [09]
j.     "             "      'snowhite' for Kali Linux [10]

(( Bay-area localsite [11] for all but the first two as the proverbial
Mirror-Mirror-on-the-Wall to decide the Fairest Debian-based Distro of
Them All? ;-} LOL! ))

2. amd64 virtualbox host OS 'lilredrdhd'
32bit guest machines....
k. VBox-label and guestname 'redrdhd' for Slackware Linux[12]
l.     "             "      'grandma' for Puppy Linux[13]
m.     "             "      'evilwolf' for Peppermint OS[14]
n.     "             "      'hunter' for G4OS[15]
o.     "             "      'passerby1' for NixOS[16]
p.     "             "      'passerby2' for Alpine Linux[17]
q.     "             "      'passerby3' for Void Linux[18]

Other remaining 32bit distros suggestions and recommendations are most
certainly welcome :-)


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