atrtc —
AT
Real-Time Clock (RTC) driver
This driver is a mandatory part of i386/amd64 kernels.
The following tunables are settable from the
loader(8):
-
hint.atrtc.X.clock
- controls event timers functionality support. Setting to
0, disables it. Default value is 1.
- hw.atrtc.enable
- Forces enabling or disabling of the device(s). Setting to
0 disables it, setting to 1 enables it, bypassing any platform
configuration hints. Default value is -1 (autodetect).
This 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.
apic(4),
attimer(4),
eventtimers(4),
hpet(4)