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Date:      Fri, 5 Oct 2012 14:23:13 +0300
From:      Konstantin Belousov <kostikbel@gmail.com>
To:        Dag-Erling Sm??rgrav <des@des.no>
Cc:        Garrett Cooper <yanegomi@gmail.com>, Dimitry Andric <dimitry@andric.com>, Andriy Gapon <avg@freebsd.org>, freebsd-arch@freebsd.org
Subject:   Re: x86 boot code build
Message-ID:  <20121005112313.GN35915@deviant.kiev.zoral.com.ua>
In-Reply-To: <86txu9l4z9.fsf@ds4.des.no>
References:  <506C385C.3020400@FreeBSD.org> <506DEB4C.5020508@andric.com> <86haq9hq2c.fsf@ds4.des.no> <20121005033244.GL35915@deviant.kiev.zoral.com.ua> <86y5jll7kc.fsf@ds4.des.no> <CAGH67wQqs9DJoy0LSgKi1_wMFyrHUE69Dgc2dht7q8VXDVAeQQ@mail.gmail.com> <86txu9l4z9.fsf@ds4.des.no>

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On Fri, Oct 05, 2012 at 10:04:26AM +0200, Dag-Erling Sm??rgrav wrote:
> Garrett Cooper <yanegomi@gmail.com> writes:
> > I would target the appropriate architecture (amd64) where it matters
> > (amd64), and target the lowest sane common denominator on i386. In
> > reality, what does a couple MB mean on amd64 vs i386?
>=20
> 1) Nobody mentioned amd64 - this is about i386.
>=20
> 2) It's not a question of *size* but of *performance*.  By targeting the
>    least capable platform that our users are likely to encounter
>    (pentium-mmx) instead of one which is virtually eradicated (486), we
>    can use features that are available on the former but not the latter.
So what ISA additions do you expect to get advantage of by switching
to pentium-mmx from 486 ? As I already said, I am not aware of any.

I can only think of cmpxchg8b, which would eventually allow to implement
64bit atomics on i386, but this has nothing to do with the compiler.
>=20
>    Someone said they'd like to target SSE2, but that would leave many
>    common embedded systems out in the cold.  If we do that, we should
>    provide two sets of binaries; one set for sse2-capable machines
>    (which covers all i386 desktop and server machines made in the last
>    ten years) and one set for pentium-mmx (which covers the soekris and
>    other popular SFF / embedded systems).
>=20
> DES
> --=20
> Dag-Erling Sm??rgrav - des@des.no

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