Re: perspectives on 32 bit vs 64 bit
Pointers are 64-bits in 64-bit mode.
The current generation AMD64 MMUs can only handle 64-bit pointers in
which the high-order 17 bits are all the same (40 bits of
information).
Software won't have to be re-written when AMD64 chips get larger MMUs, though.
(Of course, if the software is hard-coded to limit itself to 1/2 TB
user-space memory, it will still be limiting itself.)
-Karl
On 9/30/05, Brett Viren <bv@bnl.gov> wrote:
> lsorense@csclub.uwaterloo.ca (Lennart Sorensen) writes:
>
> > A 64bit application has 64bit memory pointers,
>
> I thought opteron memory was less than 64 bit wide. I'm remembering
> reading somewhere (here?) it was 40 bits.
>
> > so it can address much more than 4GB of memory.
>
> True in either case.
>
> -Brett.
>
>
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