nvram(7)                                                 nvram(7)



     NAME
          nvram - nonvolatile memory/time of day clock interface

     DESCRIPTION
          The device /dev/nvram provides access to the real time clock
          chip  on  the Macintosh II system board.  This chip contains
          256 bytes of nonvolatile memory  (memory  that  retains  its
          contents  when  the  system's power is turned off).  It also
          contains a time of day clock.

          The special device /dev/nvram can be read by anyone.  It re-
          turns  up  to  256 bytes.  The bytes are the contents of the
          nonvolatile RAM.  In order to write to /dev/nvram, you  must
          be the superuser (root).

          If the device is already open, an attempt to  open  it  will
          return  the  error  EBUSY.  This is to ensure that a process
          can perform read-modify-write operations on the device.   If
          an  open  fails  with EBUSY, the process should wait a while
          and then try again.  After  an  open  succeeds,  the  device
          should be kept open only as long as is necessary.

     WARNINGS
          Care should be taken in writing this device.  Since the con-
          tents  of  the nonvolatile RAM are defined by Apple and used
          by many parts of both A/UX and the Macintosh operating  sys-
          tem,  indiscriminate writing could cause your system to mal-
          function.  Usually you should use the utilities provided  to
          manipulate the nvram contents.

     FILES
          /dev/nvram
          /usr/include/sys/nvram.h

     SEE ALSO
          date(1), stime(2), time(2).



















     April, 1990                                                     1