.\" $NetBSD: mem.4,v 1.3 2003/08/07 10:31:04 agc Exp $
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.\"	from: @(#)mem.4	5.3 (Berkeley) 5/2/91
.\"
.Dd July 28, 1995
.Dt MEM 4 acorn32
.Os
.Sh NAME
.Nm mem ,
.Nm kmem
.Nd memory files
.Sh DESCRIPTION
The special file
.Nm /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
.Nm /dev/mem
are allowed.
.Pp
Kernel virtual memory is accessed through the interface
.Nm /dev/kmem
in the same manner as
.Nm /dev/mem .
Only kernel virtual addresses that are currently mapped to memory are allowed.
.Pp
On
.Tn Acorn RiscPC, A7000(+) and RC7500 systems
the
.Tn I/O
memory space (podule space and SuperIO) begins at physical address 0x03000000
and runs to 0x033fffff.
On the RiscPC, EASI space runs from 0x08000000 to 0x0fffffff.
The
per-process data
size
for the current process
is
.Dv UPAGES
long, and starts at VM_MAXUSER_ADDRESS.
.Sh FILES
.Bl -tag -width Pa -compact
.It Pa /dev/mem
.It Pa /dev/kmem
.El
.Sh HISTORY
The
.Nm mem ,
.Nm kmem
files appeared in
.At v6 .