[PD] 64 bit PD

Mathieu Bouchard matju at sympatico.ca
Tue Sep 7 07:53:15 CEST 2004

On Mon, 6 Sep 2004, thewade wrote:
> > Is there any advantage to using pure data on a 64 bit machine (if it
> > works)?  
> > Or does the 64bit just mean more precise calculations?
> 64 bit simply means that programs are able to address larger blocks of
> memory. It may also mean more precise numbering if by default ints are
> 32 or 64 bits instead of 16, but I think thats a compiler thing, not a
> hardware thing.
> char=8bits
> int=16bits
> float=32
> double=64 (I think)

Int is 32 bits, unless you compile for DOS or some kind of old
architecture, eg Commodore-64 or DEC PDP-6 ...

You may try it with this very small C program:
#include <stdio.h>
#define z(T) printf("sizeof(%s)=%d\n",#T,sizeof(T));
int main(void){z(char)z(short)z(int)z(long)z(long long)
z(float)z(double)z(long double)z(void*)z(wchar_t)
return 0;}

just remove any parts not supported by your compiler, if any.

> There might in the future be something like write combining where two
> sets of 32 bit values are combined, as it takes just one cpu cycle to
> move 64 bits as opposed to two cycles for normal x86 machines.

This is supported by the P1 and all 586-type machines, and is pretty much
_the_ definition of a 586-type machine. Guess why those CPUs had 64-bit
busses back then. However they don't use SIMD for that kind of job, they
use "superscalar execution", which is about executing two separate
instructions at once.

Mathieu Bouchard                       http://artengine.ca/matju

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