1.\" $NetBSD: mem.4,v 1.6 2002/01/15 02:08:49 wiz Exp $ 2.\" 3.\" Copyright (c) 1980, 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 vax 38.Os 39.Sh NAME 40.Nm mem , 41.Nm kmem , 42.Nm kUmem 43.Nd memory files 44.Sh DESCRIPTION 45The special file 46.Nm /dev/mem 47is an interface to the physical memory of the computer. 48Byte offsets in this file are interpreted as physical memory addresses. 49Reading and writing this file is equivalent to reading and writing 50memory itself. 51Only offsets within the bounds of 52.Nm /dev/mem 53are allowed. 54.Pp 55Kernel virtual memory is accessed through the interface 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.Pp 61The file 62.Nm /dev/kUmem 63also refers to kernel virtual memory, 64but may be used to access areas mapped to 65.Tn UNIBUS 66address space 67and other 68.Tn I/O 69areas. 70It forces all accesses to use word (short integer) accesses. 71.Pp 72On the 73.Tn VAX 7411/780, 75the 76.Tn I/O 77space base address is 7820000000(16); 79on an 11/750 80the 81.Tn I/O 82space addresses are of the form fxxxxx(16). 83On all 84.Tn VAX Ns 'en 85the 86per-process data 87size 88for the current process 89is 90.Dv UPAGES 91long and ends at the virtual address 80000000(16). 92.Sh FILES 93.Bl -tag -width Pa -compact 94.It Pa /dev/mem 95.It Pa /dev/kmem 96.It Pa /dev/kUmem 97.El 98.Sh HISTORY 99The 100.Nm mem , 101.Nm kmem 102files appeared in 103.At v6 . 104The file 105.Nm kUmem 106appeared in 107.Bx 3.0 . 108