anchor.diff:    command-list
     received-fis
     command-table
  -  (irq-latch (sup:make-event :name "AHCI Port IRQ Notifier"))
  +  irq-latch
  +  irq-timeout-timer
  +  irq-watcher
     atapi-p
     cdb-size
     lba48-capable
  
positive.code:     ;; Start command 1.
      (setf (ahci-port-register ahci port +ahci-register-PxCI+) 1)
      ;; Wait for it... Wait for it...
      (sup:event-wait irq-latch)))
  
  (defun ahci-initialize-port (ahci port)
    ;; Disable Command List processing and FIS RX.
  
negative.code: 
  (defun ahci-run-command (ahci port command)
    (let* ((port-info (ahci-port ahci port))
           (irq-latch (ahci-port-irq-latch port-info))
           (irq-timeout-timer (ahci-port-irq-timeout-timer port-info))
           (irq-watcher (ahci-port-irq-watcher port-info)))
      ;; Reset PRDBC, stop it accumulating over commands. I'm not sure how the HBA actually uses this,
      ;; if it keeps track of DMA progress or if it's just for reporting.
      (setf (sup::physical-memref-unsigned-byte-32 (ahci-port-command-list port-info) +ahci-ch-PRDBC+) 0)
  