I have a 64 bit AMD system to work with for a few weeks, and I'm wondering which distros have made the most progress in adapting to a 64-bit platform. Any suggestions?

All are equivalent. Take your pick.

Well, I'm wondering about that. I've been using Arch for a while, but Arch people say that their 64-bit version is "fledgling". So I was thinking that some distros have progressed further than others.

In this case, I'm not comparing distros for anything other than 64-bit compatibility and optimization. Other questions -- package management, installation, community support, etc. -- are secondary for me right now.

Choose a distro with a bi-arch architecture. Not one that is pure 64 bit. Some distro's like SuSE will install, by default, the 32 bit versions of some packages such as firefox. You will have less problems with plugins.

That's helpful, thanks. Other than SuSE, what are some bi-arch distros? I know I could go through distrowatch.com, but I thought I'd get a jump start by asking here.

The script that starts firefox in SuSE looks at 'file /usr/lib/firefox/firefox-bin'

file /usr/lib/firefox/firefox-bin
/usr/lib/firefox/firefox-bin: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), for GNU/Linux 2.6.4, dynamically linked (uses shared libs), for GNU/Linux 2.6.4, stripped.

You might want to look at a library package or two and see if there are 64 and 32 bit versions.
rpm -ql libjpeg libjpeg-32bit
/usr/lib64/libjpeg.so.62
/usr/lib64/libjpeg.so.62.0.0
/usr/lib/libjpeg.so.62
/usr/lib/libjpeg.so.62.0.0

The two versions should install to separate directories.

---

I was looking at a Fedora Core install and comparing, but then I realized that I was looking at a 32 bit system. I hope you didn't read the possibly erroneous information I posted before editing.

-----

This reference mentions SuSE and Red Hat 9 as being bi-arch distro's.
http://isdp.nih.gov/downloads/vpn_tools.asp

If you are looking at a distro that jumps through hoops like running 32bit apps in a chroot environment, I would avoid that distro.

Thanks, jschiwal, that's the sort of specific info that will help me decide.

Fedora and Mandriva are bi-arch as well. Debian and Ubuntu are pure AMD64. That being said, Fedora can install both 32 and 64 bit firefox but I found it so annoying having to switch from one to use flash and then to another to use mplayer that I ended up installing nspluginwrapper and now I can have all those plugins in firefox 64 bit. The only reason I still prefer a bi-arch system is because I have a few programming IDEs that simply will not run on a pure 64 bit system.

Speaking from my personal experience I would say try Fedora 7 x86_64. Again this may be a biased opinion, but I've been using Fedora since a little more than a year, FC5, FC6 then and Fedora 7 now and I find it to be very impressive. Yes its a bi-arch distro. However may be the (flash)plugin issue in Firefox, I run the 32-bit version, which I got very easily, didn't bother about hacking, searching etc, just downloaded the tar file, extracted and put a link to the executable wherever I needed.

And yes it can be installed purely as 64bit, "linux x86_64" at the installation prompt.