gistfile1.el

(defvar R1)
(defvar R2)
(defvar R3)
(defvar R4)

(defun snesrand (&optional seed)
  "Based on
https://github.com/optixx/snes/blob/master/libs/RANDOM.ASM "
  (cond (seed
         (setq R1 (ash seed -12))
         (setq R2 (ash seed -8))
         (setq R3 (ash seed -4))
         (setq R4 seed)
         R1)
        (t
         (setq R4 R3)
         (setq R3 R2)
         (setq R2 R1)
         (cond ((> R2 R3)
                (setq R1 (+ R3 R4)))
               (t
                (setq R1 (+ R2 R4))))
         R1)))