1.\" Copyright (c) 1992, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This software was developed by the Computer Systems Engineering group 5.\" at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and 6.\" contributed to Berkeley. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed by the University of 19.\" California, Berkeley and its contributors. 20.\" 4. Neither the name of the University nor the names of its contributors 21.\" may be used to endorse or promote products derived from this software 22.\" without specific prior written permission. 23.\" 24.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34.\" SUCH DAMAGE. 35.\" 36.\" from: @(#)mem.4 8.1 (Berkeley) 6/5/93 37.\" $NetBSD: mem.4,v 1.1 1999/11/28 17:39:47 scw Exp $ 38.\" 39.Dd November 28, 1999 40.Dt MEM 4 mvme68k 41.Os 42.Sh NAME 43.Nm mem , 44.Nm kmem 45.Nd main memory 46.Sh DESCRIPTION 47The file 48.Nm /dev/mem 49is an interface to the physical memory of the computer. 50Byte offsets in this file are interpreted as physical memory addresses. 51Reading and writing this file is equivalent to reading and writing 52memory itself. 53An error will be returned if an attempt is made to reference 54an offset outside of 55.Nm /dev/mem . 56.Pp 57Kernel virtual memory is accessed via the file 58.Nm /dev/kmem 59in the same manner as 60.Nm /dev/mem . 61Only kernel virtual addresses that are currently mapped to memory are allowed. 62.Pp 63On the 64.Tn Motorola 65MVME series of single board computers, 66physical memory may be discontiguous; 67kernel virtual memory begins at 68.Ad 0x00008000 . 69.Sh FILES 70.Bl -tag -width /dev/kmem -compact 71.It Pa /dev/mem 72.It Pa /dev/kmem 73.El 74.Sh HISTORY 75The files 76.Nm mem 77and 78.Nm kmem 79appeared in 80.At v6 . 81