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MEM(4)            BSD Programmer's Manual (VAX Architecture)            MEM(4)

N\bNA\bAM\bME\bE
    m\bme\bem\bm, k\bkm\bme\bem\bm, k\bkU\bUm\bme\bem\bm - memory files

D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
    The special file /\b/d\bde\bev\bv/\b/m\bme\bem\bm is an interface to the physical memory of the
    computer.  Byte offsets in this file are interpreted as physical memory
    addresses.  Reading and writing this file is equivalent to reading and
    writing memory itself.  Only offsets within the bounds of /\b/d\bde\bev\bv/\b/m\bme\bem\bm are
    allowed.

    Kernel virtual memory is accessed through the interface /\b/d\bde\bev\bv/\b/k\bkm\bme\bem\bm in the
    same manner as /\b/d\bde\bev\bv/\b/m\bme\bem\bm. Only kernel virtual addresses that are currently
    mapped to memory are allowed.

    The file /\b/d\bde\bev\bv/\b/k\bkU\bUm\bme\bem\bm also refers to kernel virtual memory, but may be used
    to access areas mapped to UNIBUS address space and other I/O areas.  It
    forces all accesses to use word (short integer) accesses.

    On the VAX 11/780, the I/O space base address is 20000000(16); on an
    11/750 the I/O space addresses are of the form fxxxxx(16). On all VAX'en
    the per-process data size for the current process is UPAGES long and ends
    at the virtual address 80000000(16).

F\bFI\bIL\bLE\bES\bS
    /dev/mem
    /dev/kmem
    /dev/kUmem

H\bHI\bIS\bST\bTO\bOR\bRY\bY
    The m\bme\bem\bm, k\bkm\bme\bem\bm files appeared in Version 6 AT&T UNIX.  The file k\bkU\bUm\bme\bem\bm ap-
    peared in 3.0BSD.

4th Berkeley Distribution        June 5, 1993                                1