Keyboard scrolling with acceleration

gistfile1.el

(setq my-scroll-counter 0)
(setq my-scroll-limit 5)
(setq my-last-scroll 0)
(setq my-scroll-interval 0.1)

(defun up1()
  (interactive)
  (let ((now (float-time)))
    (if (and (eq last-command this-command)
             (< (- now my-last-scroll) my-scroll-interval))
        (incf my-scroll-counter)
      (setq my-scroll-counter 0))
    (setq my-last-scroll now))

  (if (> my-scroll-counter my-scroll-limit)
      (scroll-up 2)
    (scroll-up 1)))

(global-set-key "!" 'up1)