scroll-conservatively variable with M-x
customize-variable RET scroll-conservatively RET and set it
to a large value like, say, 10000. For an explanation of what this
means, see Auto Scrolling in The GNU Emacs Manual.
Alternatively, use the following Lisp form in your init file (see How do I set up an init file properly?):
(setq scroll-conservatively most-positive-fixnum)