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Re: new software if moving to amd64?

On Fri, Oct 03, 2014 at 02:45:59PM -0700, Ray Andrews wrote:
> Ok thanks, that's a good start right there.  Looking at various
> blogs and such, it seems no two people can agree if the conversion
> to '64 is beneficial or even wise.  I have only 2 GB of RAM on this
> machine, so that's no motive.  I hear talk of various problems on
> the one hand, vs. claims of better performance on the other.  Can I
> sorta slide from '32 to '64 by degrees? I mean, so that whenever I
> do an upgrade it will convert what's convertible while leaving the
> rest of the system '32?  Or should I start afresh? Or should  I just
> leave this older machine alone?

64bit has twice the registers than 32bit in the case of x86, so some
programs gain some performance that way.  Also 64bit always uses SSE for
floating point, while 32bit by default uses x87 floating point which is
a lot slower.

Now 64bit does have some overhead due to the pointers being twice as big,
which means more cache use and memory bandwidth, although probably not
that much in general.

The best option will actually end up being x32 (which is 32bit programs
using the 64bit cpu so you get all the new registers and SSE floating
point, but without the pointer overhead).  Not sure how far along x32
is at this point.

Len Sorensen

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