Date: Fri, 7 Apr 2006 23:05:52 -0700 From: John-Mark Gurney <gurney_j@resnet.uoregon.edu> To: Astrodog <astrodog@gmail.com> Cc: freebsd-amd64@freebsd.org Subject: Re: extreme mem usage under amd64 arch ? Message-ID: <20060408060552.GG72485@funkthat.com> In-Reply-To: <2fd864e0604072236p2ee54649ld9d328f429005d6a@mail.gmail.com> References: <20060407172618.GC72485@funkthat.com> <200604072116.k37LGQhQ071637@lurza.secnetix.de> <2fd864e0604072236p2ee54649ld9d328f429005d6a@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Astrodog wrote this message on Sat, Apr 08, 2006 at 13:36 +0800:
> On 4/8/06, Oliver Fromme <olli@lurza.secnetix.de> wrote:
> > I guess this is the most important reason: If ints were 64
> > bits, there would be no easy way to handle 32 bit entities.
> > Not being able to handle 32 bit objects with a native data
> > type whould be a major problem, especially for an OS kernel,
> > I think.
> >
> Can an AMD64 processor actually handle 32 bits of data natively, or
> does it just knock off the last 32 bits of a 64-bit version, when its
> not in long mode?
yes, it can... infact it defaults to 32bits unless a prefix is
provided to access 64bit registers... (assuming a mode that 64bit
registers are accessable).. Though as w/ most processors, the upper
32bits are still around, just on 32bit operations they are ignored...
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20060408060552.GG72485>