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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Wed, 13 Jan 2021 12:27:01 +0200
Message-ID: <CAHp75Vf43_zqDX9K4GmkRd7fujY2zC8=LneSMFpC2qnJL_uG1A@mail.gmail.com>
Subject: Re: Old platforms: bring out your dead
To:     David Laight <David.Laight@aculab.com>
Cc:     Arnd Bergmann <arnd@kernel.org>, Willy Tarreau <w@1wt.eu>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
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On Mon, Jan 11, 2021 at 11:55 AM David Laight <David.Laight@aculab.com> wrote:
> From: Arnd Bergmann
> > Sent: 09 January 2021 21:53
> >
> > On Sat, Jan 9, 2021 at 6:56 AM Willy Tarreau <w@1wt.eu> wrote:
> > >
> > > On Fri, Jan 08, 2021 at 11:55:06PM +0100, Arnd Bergmann wrote:
> > > > * 80486SX/DX: 80386 CPUs were dropped in 2012, and there are
> > > >   indications that 486 have no users either on recent kernels.
> > > >   There is still the Vortex86 family of SoCs, and the oldest of those were
> > > >   486SX-class, but all the modern ones are 586-class.
> > >
> > > These also are the last generation of fanless x86 boards with 100% compatible
> > > controllers, that some people have probably kept around because these don't
> > > age much and have plenty of connectivity. I've used an old one a few times
> > > to plug in an old floppy drive, ISA SCSI controllers to access an old tape
> > > drive and a few such things. That doesn't mean that it's a good justification
> > > not to remove them, what I rather mean is that *if* there is no benefit
> > > in dropping them maybe we can keep them. On the other hand, good luck for
> > > running a modern OS on these, when 16MB-32MB RAM was about the maximum that
> > > was commonly found by then (though if people kept them around that's probably
> > > because they were well equipped, like that 64MB 386DX I'm having :-)).
> >
> > I think there were 486s with up to 256MB, which would still qualify as barely
> > usable for a minimal desktop, or as comfortable for a deeply embedded
> > system. The main limit was apparently the cacheable RAM, which is limited
> > by the amount of L2 cache -- you needed a rare 1MB of external L2-cache to
> > have 256MB of cached RAM, while more common 256KB of cache would
> > be good for 64MB. Vortex86SX has no FPU or L2 cache at all, but supports
> > 256MB of DDR2.
>
> There are also some newer (well less than 30 year old) cpus that are

(less than 10 years actually)

> basically 486 but have a few extra instructions - probably just cpuid
> and (IIRC) rdtsc.
> Designed for low power embedded use they won't ever have been suitable
> for a desktop - but are probably fast enough for some uses.
> I'm not sure how much keeping 486 support actually costs, 386 was a
> PITA - but the 486 fixed most of those issues.

Right, we have "last of mohicans" (to date) Intel Quark family of CPUs
(486 core + few i586 features).
This is for the embedded world and probably not for powerful use.

-- 
With Best Regards,
Andy Shevchenko