anchor.diff:         (let* ((frame (or (allocate-physical-pages 1)
                            (panic "Aiee. No memory.")))
                 (cache-addr (+ +physical-map-base+ (ash frame 12))))
  -         (dotimes (i 512)
  -           (setf (sys.int::memref-unsigned-byte-64 cache-addr i) 0))
  +         (zeroize-page cache-addr)
            (setf (sys.int::memref-t cache-addr 511) *block-cache*
                  *block-cache* cache-addr)
            (setf (sys.int::memref-unsigned-byte-64 cache-addr 0) block-id
  
positive.code:                                                         (ash 1 +page-frame-flag-cache+)))
          (cond ((logtest sys.int::+block-map-zero-fill+ block-info)
                 ;; Block is zero-filled.
                 (dotimes (i 512)
                   (setf (sys.int::memref-unsigned-byte-64 addr i) 0))
                 ;; Clear the zero-fill flag.
                 (set-address-flags address (logand block-info
                                                    sys.int::+block-map-flag-mask+
  
negative.code: (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))
  
  (declaim (inline zeroize-page))
  (defun zeroize-page (addr)
    (dotimes (i 512)
      (setf (sys.int::memref-unsigned-byte-64 addr i) 0)))
  
  (defun detect-paging-disk ()
    (dolist (disk (all-disks))
  