Copyright (c) 2010 Alexander Motin <mav@FreeBSD.org> All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the docum...
NAMEatrtc - AT Real-Time Clock (RTC) driver
SYNOPSISThis driver is a mandatory part of i386/amd64 kernels.
The following tunable is settable from the loader(8):
- hint.atrtc. X .clock
- controls event timers functionality support. Setting to 0, disables it. Default value is 1.
DESCRIPTIONThis driver uses RTC hardware to supply kernel with time-of-day clock with 1 second resolution and one event timer. This hardware uses base frequency of 32768Hz for advancing time-of-day clock and generating periodic interrupts. Interrupts could be generated with fixed number of frequencies, from 2Hz to 8192Hz, obtained by dividing base frequency by one of supported power-of-2 divisors.
Event timer provided by the driver is irrelevant to CPU power states.