4BSD/usr/man/cat4/mem.4

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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.

     Byte addresses in _m_e_m are interpreted as physical memory
     addresses.  References to non-existent locations cause
     errors to be returned.

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

     The file _k_m_e_m is the same as _m_e_m except that kernel virtual
     memory rather than physical memory is accessed.

     On PDP11's, the I/O page begins at location 0160000 of _k_m_e_m
     and per-process data for the current process begins at
     0140000.  On VAX's the I/O space begins at physical address
     20000000(16) and per-process data for the current process is
     at virtual 7ffff400(16).

FILES
     /dev/mem, /dev/kmem

BUGS
     On PDP11's and VAX's, memory files are accessed one byte at
     a time, an inappropiate method for some device registers.
























Printed 11/10/80                                                1