docs on Ubuntu AMD64 design?

I just noticed that Ubuntu does NOT seem to be using the "pure 64 bit"
used by Debian AMD64.  Instead, Ubuntu seems to provide additional 32
bit compatibility libraries.

However, so far I haven't found any info at all on just what Ubuntu's
AMD64 library design is exactly, nor how it differs from Debian's (or
Red Hat's, Or Novell's...)  Are there developer docs on that?  Where
should I look for such info?

I found these related teams on the Wiki:

  http://www.ubuntulinux.org/community/teams/amd64    
  http://www.ubuntulinux.org/community/teams/server 

But I don't see any actual about those teams at all, no email lists,
nothing.  Is there somewhere else I should look?


Some Debian AMD64 docs:

  http://www.debian.org/ports/amd64/
  https://alioth.debian.org/docman/view.php/30192/21/debian-amd64-howto.html

-- 
Andrew Piskorski <atp at piskorski.com>
http://www.piskorski.com/