Bug 20738

mc146818A is writtend as mc14618a. That should be corrected.
And some description are added to i8254 and TSC.

Fix: 

.Xr getitimer 2 ,--IFKr1FNzi3rfze5KqWP1xniK7xIBEtbuRkXSLalFkhL28DjJ
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*** clocks.7.old        Sun Jul 30 10:53:34 2000
--- clocks.7    Mon Aug 21 06:32:11 2000
***************
*** 102,108 ****
  .Xr sysctl 3
  or by reading it from the header in the profiling data file.
  .It
! The mc14618a clock.  This is a real clock with a nominal frequency of
  32768.  It is divided down to give the statistic clock and the profiling
  clock.  It isn't available to applications.
  .It
--- 102,108 ----
  .Xr sysctl 3
  or by reading it from the header in the profiling data file.
  .It
! The mc146818A clock.  This is a real clock with a nominal frequency of
  32768.  It is divided down to give the statistic clock and the profiling
  clock.  It isn't available to applications.
  .It
***************
*** 113,132 ****
  .Xr gettimeofday 2 ,
  .Xr select 2 ,
  .Xr getitimer 2 ,
! etc...  This is the clock that should normally be used
! by BSD applications.
  .It
  The i8254 clock.  This is a real clock/timer with a nominal frequency of
! 1193182.  It is divided down to give the scheduling clock.  It isn't
! available to applications.
  .It
  The TSC clock (64-bit register) on fifth-generation or later x86 systems.
  This is a real clock with a frequency that is equivalent to the number of
  cycles per second of the CPU(s).
! Its frequency can be found using the sysctl
! .Sy machdep.tsc_freq .
  It is used to interpolate between values of the scheduling clock.
! It is only available to applications in a purely machine-dependant manner.
  .El
  .Pp
  Summary: if
--- 113,136 ----
  .Xr gettimeofday 2 ,
  .Xr select 2 ,! etc...  It could be implemented by the i8254 clock or the TSC clock. 
! This is the clock that should normally be used by BSD applications.
  .It
  The i8254 clock.  This is a real clock/timer with a nominal frequency of
! 1193182.  It has three independent time counters to be used. It 
! is divided down to give the scheduling clock.  It isn't available 
! to applications.
  .It
  The TSC clock (64-bit register) on fifth-generation or later x86 systems.
  This is a real clock with a frequency that is equivalent to the number of
  cycles per second of the CPU(s).
! Its frequency can be found using the sysctl 
! .Sy machdep.tsc_freq ,
! if it is available.
  It is used to interpolate between values of the scheduling clock.
! It could be accessed via PMIOTSTAMP request of 
! .Xr perfmon 4 .
! 
  .El
  .Pp
  Summary: if
***************
*** 140,146 ****  .Xr select 2 ,
  .Xr clock 3 ,
  .Xr moncontrol 3 ,
! .Xr times 3
  .Sh AUTHORS
  This man page has been written by
  .ie t J\(:org Wunsch
--- 144,151 ----
  .Xr select 2 ,
  .Xr clock 3 ,
  .Xr moncontrol 3 ,
! .Xr times 3 ,
! .Xr perfmon 4
  .Sh AUTHORS
  This man page has been written by
  .ie t J\(:org Wunsch