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nvram(4/amd64) driver for reading PC NVRAM contents
nvram(4/i386) driver for reading PC NVRAM contents
nvram(4/mvme88k) Mostek MK48T0x battery-backed realtime clock

NVRAM(4) Device Drivers Manual (amd64) NVRAM(4)

nvram
driver for reading PC NVRAM contents

pseudo-device nvram 1

The nvram device provides read-only access to the non-volatile memory contained in the MC146818 real-time clock.
This data is provided as a seekable character device, /dev/nvram. Checksums of the NVRAM contents are calculated over bytes 2 to 31 and stored in byte 32. A valid checksum is required for the driver to initialize.

 
 
/dev/nvram
 

nvram support was originally included in OpenBSD 3.7.
August 2, 2007 OpenBSD-5.4