Why is amd64 late?

Mon Sep 17 11:09:44 UTC 2007

Hi,
Why is the amd64 release/tribe always late?
My favorite example is about the Xen support:
http://packages.ubuntu.com/gutsy/base/linux-image-2.6.22-11-xen
It is i386 only at the moment...
As far as I know, Ubuntu tries to be up to date and tries to support the
maximum of hardware as possible. And recent hardware is mostly amd64.
So, I probaly missed something: the reason.
Would you help me to understand?

Thank you. :)