1.\" $NetBSD: mem.4,v 1.4 1997/10/19 12:57:21 mrg Exp $ 2.\" 3.\" Copyright (c) 1990, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" from: @(#)mem.4 8.1 (Berkeley) 6/5/93 35.\" 36.Dd June 5, 1993 37.Dt MEM 4 hp300 38.Os 39.Sh NAME 40.Nm mem , 41.Nm kmem 42.Nd main memory 43.Sh DESCRIPTION 44The file 45.Nm /dev/mem 46is an interface to the physical memory of the 47computer. 48Byte offsets in this file are interpreted as physical memory addresses. 49Reading and writing this file is equivalent to reading and writing 50memory itself. 51An error will be returned if an attempt is made to reference 52an offset outside of 53.Nm /dev/mem . 54.Pp 55Kernel virtual memory is accessed via the file 56.Nm /dev/kmem 57in the same manner as 58.Nm /dev/mem . 59Only kernel virtual addresses that are currently mapped to memory are allowed. 60.Sh HP300 61On the 62.Tn HP300 , 63the last byte of physical memory is always 64.Li 0xFFFFFFFF . 65Therefore, on an 66.Tn HP300 67with 688Mb of memory, physical memory would start 69at 70.Li 0xFF800000 . 71On the 72.Tn HP300 , 73kernel virtual memory runs from 74.Li 0 75to about 76.Li 0x2400000 . 77.Sh FILES 78.Bl -tag -width /dev/kmem -compact 79.It Pa /dev/mem 80.It Pa /dev/kmem 81.El 82.Sh HISTORY 83The files 84.Nm mem 85and 86.Nm kmem 87appeared in 88.At v6 . 89