Status of NX bit support.

[Steve Kargl]

On Mon, Apr 03, 2006 at 05:23:13PM -0400, Mike Jakubik wrote:
> Steve Kargl wrote:
> >On Mon, Apr 03, 2006 at 05:06:07PM -0400, Mike Jakubik wrote:
> >  
> >>John Baldwin wrote:
> >>    
> >>>On Sunday 02 April 2006 14:48, Mike Jakubik wrote:
> >>>      
> >>>>I was wondering what the status of the NX bit support is. Is the pmap.c 
> >>>>code still broken or is support enabled and functioning by default?
> >>>>        
> >>>I don't think the status has changed.
> >>>      
> >>Well that sucks.. I guess then there really is no reason for someone to 
> >>run in amd64 mode unless you need more than 4GB of ram.
> >>    
> >
> >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?
> >
> 
> Yes, but doesn't the software have to be written to take advantage of 
> these? (What about Intels 64bit extensions, do they have the same extra 
> registers as the amd cpus?). As far as i can see so far, amd64 mode just 
> eats more memory.

Do you do a large amount of number crunching?  AMD paid
for work on GCC to optimize gcc's machine description.  I've
never tried a benchmark of FreeBSD i386 versus FreeBSD amd64
for number crunching.  It would be interesting to see a 
comparison of math/atlas on amd64 hardware under FreeBSD i386
and amd64.  Someday, if I have time ....

The livermore loops may also be interesting.

-- 
Steve