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Re: Debian for x86-64 (AMD Opteron)

Philippe Troin wrote:

Ben Collins <bcollins@debian.org> writes:

On Wed, Apr 09, 2003 at 09:58:04PM +0200, Arnd Bergmann wrote:
Note that the x86_64 is special: It would be relatively easy to bootstrap
a port on the actual hardware, but doing it right requires changing _all_
library packages as well as many other packages. The problem is that
we want binaries to be compatible with i386 as well as with other x86_64
distributions and that requires the installation of both 32 and 64 bit
libraries at the same time.
IMO, the right way is just like ia64 is doing. 64bit userspace with an
ia32 subarch installable. Best part about this is that you can use
almost everything ia64 is doing already. In fact, if dpkg could support
ia32 packages as a subarch for ia64 and x86_64, the packages could be
installable on both as-is.

I definitely prefer everything 64-bit with optionally 32-bit rather
than the other way around. Otherwise what's the point?

Plus, as another poster wrote, 64-bit executable might end-up being
faster because of the extra 64-bit-only registers.


Then again, it's more likely to end up SLOWER as loading 64 bit values from memory into registers is going to go at half the speed of loading 32 bit values, just based on bus bandwidth alone. If the system you're supporting does BOTH 32 & 64 bit at the same time, then unless you need > 2GB access, 32bit is probably going to be the way to go.

I'm not sure how your logic works out that a 64 bit reg is going to be faster than a 32bit one. Or do you mean simply you're expecting a speedu because there are MORE 64 bit registers tahn 32 bit registers?



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