4.3BSD-Reno/share/man/cat4/vax/mem.0
MEM(4) 1986 MEM(4)
NNAAMMEE
mem, kmem - main memory
DDEESSCCRRIIPPTTIIOONN
_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.
The file _k_m_e_m is the same as _m_e_m except that kernel virtual
memory rather than physical memory is accessed. Only kernel
virtual addresses that are mapped to memory are allowed.
The file _k_U_m_e_m 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. Examining and patching device registers
is likely to lead to unexpected results when read-only or
write-only bits are present.
On VAX 11/780 the I/O space begins at physical address
20000000(16); on an 11/750 I/O space addresses are of the
form fxxxxx(16). On all VAX'en per-process data for the
current process is UPAGES long, and ends at virtual address
80000000(16).
FFIILLEESS
/dev/mem
/dev/kmem
/dev/kUmem
Printed 7/27/90 May 1