1.\" $NetBSD: mem.4,v 1.6 2003/08/07 10:31:06 agc 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. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" from: @(#)mem.4 8.1 (Berkeley) 6/5/93 31.\" 32.Dd June 5, 1993 33.Dt MEM 4 hp300 34.Os 35.Sh NAME 36.Nm mem , 37.Nm kmem 38.Nd main memory 39.Sh DESCRIPTION 40The file 41.Nm /dev/mem 42is an interface to the physical memory of the 43computer. 44Byte offsets in this file are interpreted as physical memory addresses. 45Reading and writing this file is equivalent to reading and writing 46memory itself. 47An error will be returned if an attempt is made to reference 48an offset outside of 49.Nm /dev/mem . 50.Pp 51Kernel virtual memory is accessed via the file 52.Nm /dev/kmem 53in the same manner as 54.Nm /dev/mem . 55Only kernel virtual addresses that are currently mapped to memory are allowed. 56.Sh HP300 57On the 58.Tn HP300 , 59the last byte of physical memory is always 60.Li 0xFFFFFFFF . 61Therefore, on an 62.Tn HP300 63with 648MB of memory, physical memory would start 65at 66.Li 0xFF800000 . 67On the 68.Tn HP300 , 69kernel virtual memory runs from 70.Li 0 71to about 72.Li 0x2400000 . 73.Sh FILES 74.Bl -tag -width /dev/kmem -compact 75.It Pa /dev/mem 76.It Pa /dev/kmem 77.El 78.Sh HISTORY 79The files 80.Nm mem 81and 82.Nm kmem 83appeared in 84.At v6 . 85