| MEM(4) | Device Drivers Manual (vax) | MEM(4) | 
mem, kmem,
  kUmem —
/dev/mem 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
  /dev/mem are allowed.
Kernel virtual memory is accessed through the interface
    /dev/kmem in the same manner as
    /dev/mem. Only kernel virtual addresses that are
    currently mapped to memory are allowed.
The file /dev/kUmem 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).
mem, kmem files appeared in
  Version 6 AT&T UNIX. The file
  kUmem appeared in 3.0BSD.
| June 5, 1993 | NetBSD 10.1 |