anchor.diff:  (defun page-present-p (page-table index)
     (logtest +page-table-present+
              (page-table-entry page-table index)))
  +
  +(declaim (inline address-l4-bits address-l3-bits address-l2-bits address-l1-bits))
  +(defun address-l4-bits (address) (ldb (byte 9 39) address))
  +(defun address-l3-bits (address) (ldb (byte 9 30) address))
  +(defun address-l2-bits (address) (ldb (byte 9 21) address))
  +(defun address-l1-bits (address) (ldb (byte 9 12) address))
   
   (defun detect-paging-disk ()
     (dolist (disk (all-disks))
  
positive.code:                                                                           sys.int::+block-map-present+))
                 (zero-cached-block id))
               (read-cached-block id))))
      (let* ((bml4e (ldb (byte 9 39) address))
             (bml3e (ldb (byte 9 30) address))
             (bml2e (ldb (byte 9 21) address))
             (bml1e (ldb (byte 9 12) address))
             (bml4 (read-cached-block *bml4-block*))
             (bml3 (read-level bml4 bml4e))
             (bml2 (read-level bml3 bml3e))
  
negative.code:                                                                             sys.int::+block-map-present+))
                   (zero-cached-block id))
                 (read-cached-block id))))
        (let* ((bml4e (address-l4-bits address))
               (bml3e (address-l3-bits address))
               (bml2e (address-l2-bits address))
               (bml1e (address-l1-bits address))
               (bml4 (read-cached-block *bml4-block*))
               (bml3 (read-level bml4 bml4e))
               (bml2 (read-level bml3 bml3e))
  