Copyright (c) 2010 iXsystems, Inc.
All rights reserved.
written by: Xin LI <delphij@FreeBSD.org>
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$FreeBSD$
.Dd February 8, 2010 .Dt NVRAM 4 .Os .Sh NAME .Nm nvram .Nd "non-volatile RAM" .Sh SYNOPSIS To compile this driver into the kernel, place the following line in your kernel configuration file: d -ragged -offset indent .Cd "device nvram" .Ed
p Alternatively, to load the driver as a module at boot time, place the following line in .Xr loader.conf 5 : d -literal -offset indent nvram_load="YES" .Ed .Sh DESCRIPTION The .Nm driver provides access to BIOS configuration NVRAM on i386 and amd64 systems.
p PC motherboard uses a small non-volatile memory to store BIOS settings which is usually part of its clock chip and sometimes referred as .Dq CMOS SRAM . This driver exposes bytes 14 through 128 of the NVRAM, or a total of 114 bytes, at offset zero of the device file
p This driver is useful for cloning machines that shares the same hardware configuration and need same BIOS setting tweaks. .Sh IMPLEMENTATION NOTES The BIOS NVRAM's bytes 16 through 31 are checksummed at byte 32. This driver .Em does not take care for these checksums. .Sh EXAMPLES Backup existing BIOS NVRAM to
a nvram.bin :
p .Dl dd if=/dev/nvram of=nvram.bin
p Restore BIOS NVRAM from
a nvram.bin :
p .Dl dd if=nvram.bin of=/dev/nvram .Sh SEE ALSO .Xr dd 1 .Sh HISTORY The .Nm device driver first appeared in .Fx 6.4 . .Sh AUTHORS .An -nosplit The .Nm device driver was written by .An Peter Wemm . This manual page was written by .An Xin LI .