Everett M. Greene wrote:
> "Darin Johnson" <d...@usa.net> writes:
> > Arlet wrote:
>
> > > I've worked with ARM processors which did have such a little/big endian
> > > switch.
> >
> > Some PowerPCs have this also.  ...
> >
> > The only reason I can think of for changing the natural endianness
> > of a processor is when you need compatibility with shared processors,
> > or you have a huge base of software that can't easily be made
> > portable.  Otherwise it's better to stick with the natural endianness
> > of the processor in question.
>
> If it's switchable, which is the "natural" endiness?

Since it's an architectural property (user model), it depends on the
switch.

Everett M. Greene wrote:
> If it's switchable, which is the "natural" endiness?

The endianness that's compatible with existing software.  The
little-endian mode in many PowerPCs is a bit strange, since
it just manipulates address bits, which is a bit confusing.  Ie, it's
more of a data conversion convenience than an inherent state of
operation.  So big-endian is thus the natural ordering.  Later
processors support "true little-endian", but unless there's a good
reason to use it, big-endian ends up the default for compatiblity.

I suspect that CPUs that could work either way from the very first
model wouldn't have a "natural" endianness. 

--
Darin Johnson