/share/man/man4/atrtc.4

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  1. .\" Copyright (c) 2010 Alexander Motin <mav@FreeBSD.org>
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  25. .\" $FreeBSD$
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    27. 

  27. .Dd September 17, 2010
    28. 

  28. .Dt ATRTC 4
    29. 

  29. .Os
    30. 

  30. .Sh NAME
    31. 

  31. .Nm atrtc
    32. 

  32. .Nd AT Real-Time Clock (RTC) driver
    33. 

  33. .Sh SYNOPSIS
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  34. This driver is a mandatory part of i386/amd64 kernels.
    35. 

  35. .Pp
    36. 

  36. The following tunable is settable from the
    37. 

  37. .Xr loader 8 :
    38. 

  38. .Bl -ohang
    39. 

  39. .It Va hint.atrtc. Ns Ar X Ns Va .clock
    40. 

  40. controls event timers functionality support. Setting to 0, disables it.
    41. 

  41. Default value is 1.
    42. 

  42. .El
    43. 

  43. .Sh DESCRIPTION
    44. 

  44. This driver uses RTC hardware to supply kernel with time-of-day clock
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  45. with 1 second resolution and one event timer.
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  46. This hardware uses base frequency of 32768Hz for advancing time-of-day clock
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  47. and generating periodic interrupts.
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  48. Interrupts could be generated with fixed number of frequencies, from 2Hz to
    49. 

  49. 8192Hz, obtained by dividing base frequency by one of supported power-of-2
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  50. divisors.
    51. 

  51. .Pp
    52. 

  52. Event timer provided by the driver is irrelevant to CPU power states.
    53. 

  53. .Sh SEE ALSO
    54. 

  54. .Xr apic 4 ,
    55. 

  55. .Xr attimer 4 ,
    56. 

  56. .Xr eventtimers 4 ,
    57. 

  57. .Xr hpet 4
    58.