I think I might have been able to find out about this myself, but it takes some time and effort, so I ask here: What steps are needed to get 64-bits qemu running in Knoppix 7.X? In principle it should be possible, but my simplistic attempts have so far been futile.

64-bits kernel and the basic 64-bits libraries are already installed, so I can compile 64-bits programs.
What more?

I think this may be useful for many: Running (for example) 64-bits Ubuntu in a VM will let us work with 64-bits builds etc while still staying for the most part in the smoother 32-bits world. Running 64-bits Windows (for example, the version installed on my hard drive). Running 64-bits Oracle XE 11g (there is no 32-bits version for Linux), developing and testing 64-bits OS versions (like Knoppix ), cross-compiling, etc etc.