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Date:      Wed, 09 Oct 2002 17:21:00 -0700
From:      Terry Lambert <tlambert2@mindspring.com>
To:        Wes Peters <wes@softweyr.com>
Cc:        Nate Lawson <nate@root.org>, "Vladimir B. Grebenschikov" <vova@sw.ru>, arch@FreeBSD.org
Subject:   Re: using mem above 4Gb was: swapon some regular file
Message-ID:  <3DA4C7EC.F749B803@mindspring.com>
References:  <Pine.BSF.4.21.0210081209010.11243-100000@root.org> <3DA35D58.B1B5D78D@mindspring.com> <3DA4C2F1.74450081@softweyr.com>

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Wes Peters wrote:
> Terry Lambert wrote:
> > IMO, if you want a larger linear address space, instead of pretending
> > you have one, buy yourself an IA64 instead.
> 
> Or an Alpha, or a SPARC64, or a MIPS64, etc.  But they all seem to cost
> more than a PIII solution, except perhaps a Netra and you can't cram enough
> RAM in that to make a difference.

People always say this, but... the Alpha is unsuitable, because
FreeBSD on the Alpha doesn't support more than 2G of physical
RAM, because the drivers choke.  The MIPS is not an option,
because though there is a FreeBSD port, as reported at last
year's "developer summit" at Usenix, it was never integrated into
the source tree.  The SPARC64 isn't a mainstream port yet (I know
this because my patch to kdenetwork3 was adulterated to be "if Alpha",
when it should have been adulterated to "if !32_bit_x86", if at all,
because the SPARC64 and IA64 GOT will go over 64K, as well... the
problem is the 64bit vs. 32bit values, not symbol names, etc., that
causes the table size to be bigger there).

Right now, IA64 is about the only supported 64 bit architecture
that gives you the real benefit of a 64 bit address space; I guess
you can mmap a lot of stuff on the Alpha, too, up to your KVA
mapping limit, but that's not a win for this application.

-- Terry

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