anchor.diff:                  :exclusive t)
       ;; Set countdown value.
       (setf (%cntp-tval) 0)
  +    (%isb)
       ;; Enable the timer.
  -    (setf (%cntp-ctl) 1)))
  +    (setf (%cntp-ctl) 1)
  +    (%isb)))
   
   (defun get-universal-time ()
     (+ *rtc-adjust* (truncate (%cntpct) *generic-timer-rate*)))
   
   (defun sys.int::tsc ()
     ;; This isn't the cycle counter, but it's close enough for now.
  -  (%cntpct))
  +  (prog1
  +      (%cntpct)
  +    (%isb)))
   
   (defun get-high-precision-timer ()
     ;; TODO
  -  (%cntpct))
  +  (prog1
  +      (%cntpct)
  +    (%isb)))
   
   (defun high-precision-time-units-to-internal-time-units (hp-time)
     ;; TODO
  
positive.code: 
  (sys.int::define-lap-function %cntpct (())
    (mezzano.lap.arm64:mrs :x9 :cntpct-el0)
    (mezzano.lap.arm64:isb)
    (mezzano.lap.arm64:add :x0 :xzr :x9 :lsl #.sys.int::+n-fixnum-bits+)
    (mezzano.lap.arm64:ret))
  
  
negative.code: (sys.int::define-lap-function (setf %cntp-tval) ((value))
    (mezzano.lap.arm64:add :x9 :xzr :x0 :asr #.sys.int::+n-fixnum-bits+)
    (mezzano.lap.arm64:msr :cntp-tval-el0 :x9)
    (mezzano.lap.arm64:ret))
  
  (sys.int::define-lap-function %cntp-ctl (())
  