DataMuseum.dk

top - metrics - download

    Length: 1623 (0x657)
    Types: TextFile
    Notes: UNIX file
    Names: »mem.4«

└─⟦26887b7e0⟧ Bits:30009717 Comet 32 harddisk image
    └─⟦28c352965⟧ »/a« UNIX Filesystem
        └─⟦this⟧ »usr/man/man4/mem.4« 

TextFile

.ig
	@(#)mem.4	2.1	7/1/84
	@(#)Copyright (C) 1983 by National Semiconductor Corp.
..
.TH MEM 4
.SH NAME
mem, kmem \- main memory
.SH DESCRIPTION
.I Mem
is a special file that is an image of the main memory
of the computer.
It may be used, for example, to examine
(and even to patch) the system.
.PP
Byte addresses in
.I mem
are interpreted as physical memory addresses.
References to non-existent locations cause errors to be returned.
.PP
Examining and patching device registers is likely
to lead to unexpected results when read-only or write-only
bits are present.
.PP
The file
.I kmem
is the same as 
.I mem
except that kernel virtual memory
rather than physical memory is accessed.
.PP
On PDP11s,
the I/O page begins at location 0160000 of
.I kmem
and per-process data for the current process
begins at 0140000.
On a VAX 11/780 the I/O space begins at physical address 20000000(16);
on an 11/750 I/O space addresses are of the form fxxxxx(16);
on all VAXes per-process data for the current process is at virtual
7f\&f\&f\&f000(16).
On the \fISeries 32000\fP,
both the device registers
and the per-process data for the current process
are kept in virtual addresses in
.I kmem
as specified in the file
.IR /usr/include/sys/devvm.h .
.SH FILES
.nf
/dev/mem
/dev/kmem
/usr/include/sys/devvm.h
.fi
.SH BUGS
On PDP11s and VAXes,
memory files are accessed one byte at a time.
On the \fISeries 32000\fP,
memory files are accessed with a combination
of byte,
word,
and doubleword transfers,
depending on the byte count and addresses specified in the read or write call.
This is an inappropiate method for some
device registers.