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Date:      Thu, 25 May 2000 12:14:22 -0600
From:      Warner Losh <imp@village.org>
To:        Peter Wemm <peter@netplex.com.au>
Cc:        Chuck Paterson <cp@bsdi.com>, arch@FreeBSD.ORG
Subject:   Re: Preemptive kernel on older X86 hardware 
Message-ID:  <200005251814.MAA85600@harmony.village.org>
In-Reply-To: Your message of "Thu, 25 May 2000 08:27:47 PDT." <20000525152747.AFBF21CE1@overcee.netplex.com.au> 
References:  <20000525152747.AFBF21CE1@overcee.netplex.com.au>  

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In message <20000525152747.AFBF21CE1@overcee.netplex.com.au> Peter Wemm writes:
: I would not have too much trouble with a proposal that a I386_CPU and
: maybe I486_CPU becoming mutually exclusive with the 586+ stuff.  ie: if you
: will still be able to build a kernel specifically to run on a 486, but by
: default it would not fly.

I think this would be OK, so long as it buys us something.

: I think 586+ is a convenient boundary because I am not aware of many 586's
: that don't have PNPBIOS support, while 486's are mixed as they predate win95
: by a fair way.

Yes.  Lots of the SBCs in the embedded world still are 486 based due
to their cheap cost, lower power consumption and low pin counts.  I
just took plastic off a new 486 133 (AMD 5x86 133) the other day which 
was made this year.  It does have PNPBIOS support.

: Aiming for a default fresh-install target (remember, 5.0 is 6-12 months
: away) where we require minimum 586+ and PNPBIOS etc etc would simplify
: things a fair bit..  In such a scenario it should still be possible to
: build a kernel to specifically support an i486 on a non-PNP isa-only system
: without PCI etc.  I have a 486 still running and would hate to loose it for
: sentimental reasons, but I do custom builds for it anyway.  I strongly doubt
: that there will be many *fresh* 486 installs, if any at all.

But how does one upgrade then.  These older machines typically do do
freshinstalls to upgrade them.  In the village we have a spare machine 
that we upgrade by doing a fresh install, then mutate it to be one of
the other machines, then pull the trigger and take the old one down
and put the new one in to do a rolling upgrade.

Also, there will be many fresh installs onto the embedded hardware.  I 
personally just do an installworld to make these machines, but other
users might not be as sophisticated.

: But that is changing the subject. :-)
: 
: > I would have no problem saying SMP is only supported on Pentiums or
: > newer.
: 
: I don't think we support 486 SMP right now, but I could be wrong.

I think that you are right...

warner


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