Re: r343567 aka PAE vs non-PAE merge breaks i386 freebsd

On Thu, Feb 28, 2019 at 12:46 PM John Baldwin <jhb_at_freebsd.org> wrote:

> On 2/28/19 11:14 AM, Cy Schubert wrote:
> > On February 28, 2019 11:06:46 AM PST, Conrad Meyer <cem_at_freebsd.org>
> wrote:
> >> On Thu, Feb 28, 2019 at 10:32 AM Steve Kargl
> >> <sgk_at_troutmask.apl.washington.edu> wrote:
> >>> This is interesting as well.  Does this mean that amd64 is now
> >>> the only tier 1 platform and all other architectures are after
> >>> thoughts?
> >>
> >> This has been the de facto truth for years.  i386 is mostly only
> >> supported by virtue of sharing code with amd64.  There are efforts to
> >> promote arm64 to Tier 1, but it isn't there yet.  Power8+ might be
> >> another good alternative Tier 1 candidate eventually.  None have
> >> anything like the developer popularity that amd64 enjoys.
> >>
> >> Conrad
> >> _______________________________________________
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> >
> > We deprecated and removed support for 386 and 486 processors. We should
> consider removing support for low end Pentium as well. I'm specifically
> thinking of removing the workarounds like F00F. Are there any processors
> that are still vulnerable to this?
>
> We have only removed support for 386 since it didn't support cmpxchg.  We
> still
> nominally support 486s.  I don't know how well FreeBSD 13 would run on a
> 486, but
> in theory the code is still there and the binaries shouldn't die with
> illegal
> instruction faults.
>

The biggest barrier to running on a real 486 is that it's hard for FreeBSD
to fit into 32MB that was the maximum config you could have. You can barely
boot it w/o tuning, though it will still fit a few jobs if you are looking
at something super low-end with a lot of effort.

There are a few later CPUs built on basically a 486 whose chipsets could
support up to 128MB or 256MB which is enough to run FreeBSD still.

Warner