Re: "Trivial Question" - 32bit vs. 64bit vs. 32/64bit
On Thu, May 27, 2004 at 09:56:39AM +0200, Hendrik Tews wrote:
> Dear all,
>
> I would like to raise other trivial questions for which I cannot
> find answers in the AMD64 HOWTO or via google:
>
> - What does pure64 mean? When do I want pure64?
>
> - Same for biarch, what does it mean, when do I want it?
The amd64 chip is somewhat unique in that it actually supports two
different operation modes. It can be run in 32-bit mode. You can
actually buy an amd64 chip and install the existing i386 Debian
distribution and have a perfectly usable system.
It can also run in 64-bit mode. That is what the pure64 code does.
Pure64 is basically a Debian port done just like a Debian port to any
other architecture. Since this has been done many times before, and
requires nothing new from Debian, it is very easy to do and that's why
we have most of Debian compiled for pure64 already.
The amd64 chips can also run an environment that uses *both* 64-bit and
32-bit code. This may be useful for people that want to run a mostly
64-bit system but have some legacy 32-bit binaries hanging around.
Pure64 is completely 64-bit. There are no 32-bit binaries in Pure64 and
it has no built-in support for 32-bit binaries. You can still run
32-bit binaries on a Pure64 system by installing a 32-bit Debian chroot.
This is inconvenient but works.
Biarch/multiarch refers to an experimental extension to Debian that
permits a userland that has mixed 32- and 64-bit code. With biarch, it
would be possible to install those programs right alongside each other
and not really notice a difference.
However, this support requires a massive change in the way we think
about packages in Debian, and about libraries in general. Therefore,
the biarch tree is nowhere near as close to being complete as pure64
because porting is a more difficult task.
I think that most of us expect that pure64 will be the first to enter
ftp.debian.org, but once our technology improves, that tree will
naturally evolve into supporting something like biarch.
> (I just ordered a dual Opteron system and soon I have to decide
> what to install on it.)
The answer depends on what you want to do with it. If you want to run
something as a production server, or are not very experienced with
Debian, I'd suggest to start with the i386 distribution and consider
moving to 64-bit code when the amd64 distribution becomes more mature.
OTOH, if you love to tinker, start with amd64 and have fun :-)
-- John
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