64-bit RPM/APT based systems - Worth it?

[Jerry Feldman]

On Sunday 30 October 2005 4:57 pm, Ben Scott wrote:

>   From what I've read, I'm not sure how accurate that is.  AMD64 (and
> Intel's clone of it, EM64T) enable CPU modes which support a native
> address space larger then 32 bits.  Not the "32 bit window into a
> larger space" that Intel PAE provided, but true native addressing.
> You also get 64 bit registers and ops, but you had those already with
> various ISA extensions.
>
>   I say "larger address space" because I don't actually know how large
> the possible address space of AMD64 is.  Current implementations may
> not support a full 64 bits of address space.  But as I recall from my
> machine architecture course at UNH, the Alpha chips of the day didn't
> really implement a full 64 bits of address space all the time, either.
>  It's inefficient to process 64 bits of address math when you only
> need 40 bits or so.  Or so I recall.  My memory is really dusty here.
The AMD64 chip supports full 64-bit virtual address space. However, only 
52-bits are currently used for physical addressing. In 64-bit mode the 
address space is flat. (A separate address space for code, stack and data 
segments is also possible).
A 32-bit app running in a 64-bit OS runs in compatibility mode where the 
legacy 32-bit and 16-bit segmentation addresses are mapped to the lower 
32-bits of virtual address.  A 32-bit OS operates in a legacy mode. 

According to industry sources, neither Intel nor AMD will be producing 
32-bit chips after next year. I personally see AMD cutting into Intel's 
market share on personal systems and low end servers since it is a better 
performing chip than Intel's EM64T line. The high-end server market will 
see IBM, HP and Sun duke it out. 
-- 
Jerry Feldman <gaf at blu.org>
Boston Linux and Unix user group
http://www.blu.org PGP key id:C5061EA9
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