anchor.diff:  (defconstant +serial-msr-ring-indicator+ 6)
   (defconstant +serial-msr-carrier-detect+ 7)
   
  +(define-interrupt-handler serial-interrupt ()
  +  't)
  +
   (defun reset-serial-port (port &optional speed)
     (check-type speed (or null (integer 50 115200)))
     (if speed
         (setf (slot-value port 'speed) speed)
         (setf speed (serial-stream-speed port)))
     (let ((base (serial-stream-io-base port))
  +        (irq (serial-stream-irq port))
           (divisor (truncate 115200 speed)))
  -    (format t "Initializing serial port ~X, speed ~D (~D)~%" base speed divisor)
  +    (format t "Initializing serial port ~X (irq ~D), speed ~D (~D)~%" base irq speed divisor)
  +    (setf (isa-pic-irq-mask irq) t)
       (when (zerop divisor) (setf divisor 1))
       ;; Configure the port.
       (setf (io-port/8 (+ base +serial-IER+)) #x00 ; Turn off interrupts.
  
positive.code:     ;; Modem control.
      (setf (io-port/8 (+ base +serial-MCR+)) (logior +serial-mcr-data-terminal-ready+
                                                      +serial-mcr-request-to-send+
                                                      +serial-mcr-auxiliary-output-2+))))
  
  (defvar *serial-one* (make-instance 'serial-stream :base #x3F8))
  (defvar *serial-two* (make-instance 'serial-stream :base #x2F8))
  
  (defmethod sys.gray:stream-write-byte ((stream serial-stream) integer)
    (check-type integer (unsigned-byte 8))
  
negative.code: (defclass serial-stream (sys.gray:fundamental-binary-input-stream
                           sys.gray:fundamental-binary-output-stream)
    ((base :initarg :base :reader serial-stream-io-base)
     (irq :initarg :irq :reader serial-stream-irq)
     (speed :initarg :speed :reader serial-stream-speed))
    (:default-initargs :speed 38400))
  
  