NVRAM(4)               FreeBSD Kernel Interfaces Manual               NVRAM(4)

NAME
     nvram - non-volatile RAM

SYNOPSIS
     To compile this driver into the kernel, place the following line in your
     kernel configuration file:

           device nvram

     Alternatively, to load the driver as a module at boot time, place the
     following line in loader.conf(5):

           nvram_load="YES"

DESCRIPTION
     The nvram driver provides access to BIOS configuration NVRAM on i386 and
     amd64 systems.

     PC motherboard uses a small non-volatile memory to store BIOS settings
     which is usually part of its clock chip and sometimes referred as "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 /dev/nvram.

     This driver is useful for cloning machines that shares the same hardware
     configuration and need same BIOS setting tweaks.

IMPLEMENTATION NOTES
     The BIOS NVRAM's bytes 16 through 31 are checksummed at byte 32.  This
     driver does not take care for these checksums.

EXAMPLES
     Backup existing BIOS NVRAM to nvram.bin:

           dd if=/dev/nvram of=nvram.bin

     Restore BIOS NVRAM from nvram.bin:

           dd if=nvram.bin of=/dev/nvram

SEE ALSO
     dd(1)

HISTORY
     The nvram device driver first appeared in FreeBSD 6.4.

AUTHORS
     The nvram device driver was written by Peter Wemm.  This manual page was
     written by Xin LI.

FreeBSD 13.1-RELEASE-p6        February 8, 2010        FreeBSD 13.1-RELEASE-p6