anchor.diff:  (defun debug-serial-stream (op &optional arg)
     (ecase op
       (:read-char (debug-serial-read-char))
  -    (:clear-input)
  +    (:clear-input (fifo-reset *debug-serial-rx-fifo*))
       (:write-char (debug-serial-write-char arg))
       (:write-string (debug-serial-write-string arg))
       (:force-output)
  
positive.code:         *debug-serial-tx-buffer* (sys.int::make-simple-vector +debug-serial-buffer-size+ :wired)
          *debug-serial-tx-buffer-head* 0
          *debug-serial-tx-buffer-tail* 0
          *debug-serial-rx-buffer* (sys.int::make-simple-vector +debug-serial-buffer-size+ :wired)
          *debug-serial-rx-buffer-head* 0
          *debug-serial-rx-buffer-tail* 0)
    ;; Initialize port.
    (let ((divisor (truncate 115200 baud)))
      (setf
  
negative.code: (defvar *debug-serial-tx-buffer*)
  (defvar *debug-serial-tx-buffer-head*)
  (defvar *debug-serial-tx-buffer-tail*)
  (defvar *debug-serial-rx-fifo*)
  (defvar *debug-serial-lock*)
  (defvar *serial-at-line-start*)
  
  