anchor.diff:          (let* ((frame (or (allocate-physical-pages 1)
                             (panic "Aiee. No memory.")))
                  (addr (+ +physical-map-base+ (ash frame 12))))
  -          (dotimes (i 512)
  -            (setf (sys.int::memref-unsigned-byte-64 addr i) 0))
  +          (zeroize-page addr)
             (setf (page-table-entry page-table index) (logior (ash frame 12)
                                                               +page-table-present+
                                                               +page-table-write+))
  
positive.code:        (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))
           (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
  
negative.code:                                                         (ash 1 +page-frame-flag-cache+)))
          (cond ((logtest sys.int::+block-map-zero-fill+ block-info)
                 ;; Block is zero-filled.
                 (zeroize-page addr)
                 ;; Clear the zero-fill flag.
                 (set-address-flags address (logand block-info
                                                    sys.int::+block-map-flag-mask+
  