Status of NX bit support.

[Andrew Reilly]

On Mon, Apr 03, 2006 at 03:23:12PM -0600, Scott Long wrote:
> Steve Kargl wrote:
> >You're joking, right?  How many registers are available for the
> >i386?  How many registers are available to an AMD64 cpu in 
> >64-bit mode?
> 
> You also get less efficient cache utilization due to the wider data
> types that are in use.  It seems to be mostly a wash between the
> advantages of more registers and the cost of lower cache efficiency.
> amd64 is nice when you need more kernel address space and/or more
> process address space.

I know I'm probably being barking mad, here, but what I'd really
like for my AMD64 workstation system is to be able to run it in
AMD64-mode, but with 32-bit pointers.  I vaguely remember
reading some early AMD bumpf that that could be a supported
configuration, somehow.  Seems like it should just be a compiler
switch, to specify 32-bit loads and stores for pointer values,
and probably some checking in the pmap system to make sure that
nothing is mapped outside the 32-bit range...

Anyone know if it's been done?  How it performs, if it's been
done?

I do a fair bit of DSP simulation work, and 64-bit long-longs
are very handy to have go fast, and more registers and
register-based calling conventions are always a good thing.  I
have no need for 64-bit addresses, at least at the process
level, and I suspect that most workstation users would be in
much the same boat...

Didn't MIPS, Sun and Apple support such an arrangement on
R4000+, SPARCv?8 and PowerPC970 (G5) systems?

Cheers,

-- 
Andrew