1.\" Copyright (c) 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" %sccs.include.redist.roff% 5.\" 6.\" @(#)mem.4 8.1 (Berkeley) 06/05/93 7.\" 8.Dd 9.Dt MEM 4 i386 10.Os 11.Sh NAME 12.Nm mem , 13.Nm kmem 14.Nd memory files 15.Sh DESCRIPTION 16The special file 17.Nm /dev/mem 18is an interface to the physical memory of the computer. 19Byte offsets in this file are interpreted as physical memory addresses. 20Reading and writing this file is equivalent to reading and writing 21memory itself. 22Only offsets within the bounds of 23.Nm /dev/mem 24are allowed. 25.Pp 26Kernel virtual memory is accessed through the interface 27.Nm /dev/kmem 28in the same manner as 29.Nm /dev/mem . 30Only kernel virtual addresses that are currently mapped to memory are allowed. 31.Pp 32On 33.Tn ISA 34the 35.Tn I/O 36memory space begins at physical address 0x000a0000 37and runs to 0x00100000. 38The 39per-process data 40size 41for the current process 42is 43.Dv UPAGES 44long, and ends at virtual 45address 0xfe000000. 46.Sh FILES 47.Bl -tag -width Pa -compact 48.It Pa /dev/mem 49.It Pa /dev/kmem 50.El 51.Sh HISTORY 52The 53.Nm mem , 54.Nm kmem 55files appeared in 56.At v6 . 57