[Beowulf] Win64 Clusters!!!!!!!!!!!!

Richard Walsh rbw at ahpcrc.org
Wed Apr 11 14:42:52 PDT 2007

Peter St. John wrote:
> On 4/11/07, *Geoff Jacobs* <gdjacobs at gmail.com
> <mailto:gdjacobs at gmail.com>> wrote:
>     Jon Forrest wrote:
>     > The examples you give are very good reasons why there is
>     > a clear need for more than 32-bits of address space for
>     > data. Again, I agree completely. But, if you read my original
>     > posting, this is not what I'm talking about. I'm talking
>     > about the need for more than 32-bits of address space for
>     > instructions ( a.k.a "text"). Why don't you run the "size"
>     > command on any of your big programs and report back what
>     > you find. My guess is that they'll be in the order
>     > of 10s of megabytes. (I agree that this method doesn't
>     > show the true run-time text-size requirements but
>     > it's a good first attempt).
>     Um, that would require distinct memory pools or some weird internal
>     mapping scheme. Not nice. Much better architecturally to have no
>     difference between pointers to instructions and pointers to data.
> Hear hear! For self-adapting softare you *can't* distinguish
> instructions from data. That may sound over-specialized but I invite
> you to consider DNA and what it does: instruct enzymes to modify DNA.
> An awful lot comes out of that process. So I don't think it's just von
> Neumann's whim. 
On the opposite side of the argument, that code/instruction set (self-modified for say about a billion years [and recombined, and mutated]) is only ~3 billion base pairs in length. If we liberally give each base pair a byte, that's only 3 billion bytes. We can quibble about what an instruction is, but also about how much of the code is used and what would be the reduced instruction set equivalent.

On the other hand, claiming that producing an application with more than 4 Gbytes of instructions is impossible seems foolish, unless there is prize money involved, of course ... ;-) ...



Richard B. Walsh

Project Manager
Network Computing Services, Inc.
Army High Performance Computing Research Center (AHPCRC)
rbw at ahpcrc.org  |  612.337.3467

>  "Making predictions is hard, especially about the future."
>   Nils Bohr

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