MEM(4)              UNIX Programmer's Manual               MEM(4)

NAME
     mem, kmem  -  main memory

DESCRIPTION
     _M_e_m is a special file that is an image of the main memory of
     the computer.  It may be used, for example, to examine, and
     even to patch the system.  _K_m_e_m is the same as _m_e_m except
     that kernel virtual memory rather than physical memory is
     accessed.  _K_m_e_m is faster than _m_e_m when the address, count,
     and base are all even.

     References to nonexistent locations return errors.

     Examining and patching device registers is likely to lead to
     unexpected results when read-only or write-only bits are
     present.

     On PDP-11s, the I/O page begins at location 0160000 of _k_m_e_m
     and the per-process data segment for the current process
     begins at 0140000.

FILES
     /dev/mem
     /dev/kmem

BUGS
     On PDP-11's, memory files are accessed one byte at a time,
     an inapproriate method for some device registers.

     On machines with ENABLE/34(tm) memory mapping boards the I/O
     page can be accessed only through _k_m_e_m.

Printed 7/31/83                                                 1