Is it possible to use new Emacsen with non-ASCII?

[Ilya Zakharevich]

I spent (again!) a lot of time trying to teach Emacs to show 8-bit data
(in a TTY).  After a lot of experiments, I see that

  emacs -q -nw --unibyte
           (standard-display-8bit 128 254)
           (set-input-mode (car (current-input-mode))
                           (nth 1 (current-input-mode))
                           '8bit)

allows one to edit the files.  Moreover, after I know the answer, I
can see that old Emacs manuals were at least mentioning these
commands.  However, newer Emacsen replaced this info by something
absolutely uncomprehensible...

Additionally, I have no idea how to make this (or something else) work
without --unibyte.  Even adding something like
(set-language-environment "Cyrillic-KOI8") all that is shown is
question marks...

Puzzled,
Ilya