2010-01-27 00:34:52 +00:00
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.\"
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.\"Copyright (c) 2010 iXsystems, Inc.
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.\"All rights reserved.
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.\" written by: Xin LI <delphij@FreeBSD.org>
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.\"
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.\"Redistribution and use in source and binary forms, with or without
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.\"modification, are permitted provided that the following conditions
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.\"are met:
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.\"1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\"2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\"THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\"ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\"IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\"ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\"FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\"DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\"OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\"HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\"LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\"OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\"SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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2010-02-08 20:53:29 +00:00
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.Dd February 8, 2010
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.Dt NVRAM 4
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2010-01-27 00:34:52 +00:00
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.Os
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.Sh NAME
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.Nm nvram
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.Nd "non-volatile RAM"
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.Sh SYNOPSIS
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To compile this driver into the kernel,
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place the following line in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "device nvram"
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.Ed
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.Pp
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Alternatively, to load the driver as a
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module at boot time, place the following line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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nvram_load="YES"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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driver provides access to BIOS configuration NVRAM on i386 and amd64
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systems.
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.Pp
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PC motherboard uses a small non-volatile memory to store BIOS settings
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which is usually part of its clock chip and sometimes referred as
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.Dq CMOS SRAM .
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This driver exposes bytes 14 through 128 of the NVRAM, or a total of
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114 bytes, at offset zero of the device file
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.Pa /dev/nvram .
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.Pp
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This driver is useful for cloning machines that shares the same hardware
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configuration and need same BIOS setting tweaks.
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.Sh IMPLEMENTATION NOTES
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The BIOS NVRAM's bytes 16 through 31 are checksummed at byte 32.
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This driver
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.Em does not
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take care for these checksums.
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.Sh EXAMPLES
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Backup existing BIOS NVRAM to
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.Pa nvram.bin :
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.Pp
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.Dl dd if=/dev/nvram of=nvram.bin
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.Pp
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Restore BIOS NVRAM from
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.Pa nvram.bin :
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.Pp
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.Dl dd if=nvram.bin of=/dev/nvram
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.Sh SEE ALSO
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.Xr dd 1
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.Sh HISTORY
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The
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.Nm
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device driver first appeared in
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.Fx 6.4 .
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.Sh AUTHORS
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.An -nosplit
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The
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.Nm
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device driver was written by
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.An Peter Wemm .
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This manual page was written by
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.An Xin LI .
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