Well, it is not so easy...
64-bit kernel loads, but it restarts.
For me it looks like loading of initrd stops at the same place, as if
there is no "video=ofonly" parameter specified.
"Calling ibm,client-architecture-support..."
Plan B was to try latest testing/wheezy,
however latest build is unsuccessful,
and ISO from 2011-07-18 has bzip bug:#633782 <mailto:633782@bugs.debian.org>
(http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=633782)
Any place to download other/older ISO images?
I'll try again experiments later...