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Re: Multiarch crazyiness



On Mon, 2007-10-22 at 15:56 -0400, Matthew Saltzman wrote:
> On Mon, 2007-10-22 at 12:20 -0400, Jesse Keating wrote:
> > On Mon, 22 Oct 2007 12:03:05 -0400
> > Matthew Saltzman <mjs CLEMSON EDU> wrote:
> > 
> > > 32-bit runtime in general?  Why?  (Not a critical "why", a genuinely
> > > curious "why"...)
> > 
> > On those arches, running 64bit code comes at a penalty.  In fact, even
> > on x86_64 there is a penalty.  Larger memory overhead.  However on
> > x86_64 the extra CPU registers gained by running in x86_64 mode
> > outweigh the memory overhead.  Not the case on ppc/sparc where there
> > are no 'extra registers' to gain.  Very little software in very few
> > situations need 64bit.
> 
> So on those archs one would want a 64-bit kernel and 32-bit apps, except
> for large-memory programs or those needing 64/128-bit numerical types
> (self-developed code, for example)?

My reservation about this kind of talk is that no assumption as to which
32/64-bit userland exists should be made anywhere but perhaps in the
default package set installed by anaconda - it is wrong to assume that
all spins of Fedora will always have a 32-bit userland on 64-bit
architectures or any such generalization ;-)

Jon.



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