[gclist] 64 bit machines and conservatism

[Charles Fiterman]

At 01:13 PM 12/15/97 -0500, you wrote:
>Concerning 64 bit machines and conservative GC, one shouldn't forget
>that what really matters is the number of bits in a pointer, not the
>size of the machine word.  For most (all?) applications out there a 32
>bit address space is still sufficient so there is no need to use 64
>bit pointers.  After all if most of your data is pointers then there
>is a savings of a factor of 2 in space (and cache efficiency) to be
>had by using 32 bit pointers.  The C compilers I have come across on
>64 bit machines all have a flag to select 32 bit pointers (for example
>"-taso" on digital UNIX).  I have used this for my Scheme compiler
>(Gambit-C) on DEC Alphas with a gain in efficiency of roughly 15%
>on memory intensive benchmarks.

64 bit machines permit a total rethink of operating system archetecture.

64 bit address space permits individual addressing of all the memory
in the world even data on music CD's in people's homes. 

So you could give all the data in the world independent addresses.
Your ram has copies of some for cashing but your disks all have
address ranges and other machines have address ranges and every
word of data in the world has its own address.


			-  
Charles Fiterman		Geodesic Systems
414 North Orleans Suite 410	Phone 312 832 1221 x223
Chicago IL 60610-4418		FAX   312 832 1230
				http://www.geodesic.com

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