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35 .Nd various system timers
40 is not part of the application interface in
43 There are many different real and virtual (timekeeping) clocks with
44 different frequencies:
45 .Bl -bullet -offset XXX
47 The scheduling clock. This is a real clock with frequency that
48 happens to be 100. It isn't available to applications.
50 The statistics clock. This is a real clock with frequency that
51 happens to be 128. It isn't directly available to applications.
55 This is a virtual clock with a frequency that happens to be 128. Its
56 actual frequency is given by the macro
60 may be floating point. Don't use
64 It is feeble compared with
66 It is provided for ANSI conformance. It is implemented by calling
68 and throwing away information and resolution.
72 This is a virtual clock with a frequency that happens to be 128. Its
73 actual frequency is given by the macro
75 (deprecated; don't use) and by
76 .Fn sysconf SC_CLK_TCK
79 Note that its frequency may be different from
85 It is feeble compared with
89 It is provided for POSIX
90 conformance. It is implemented by calling
94 and throwing away information and resolution.
96 The profiling clock. This is a real clock with frequency 1024.
102 Applications should determine its actual frequency using
104 or by reading it from the header in the profiling data file.
106 The mc14618a clock. This is a real clock with a nominal frequency of
107 32768. It is divided down to give the statistic clock and the profiling
108 clock. It isn't available to applications.
110 The microseconds clock. This is a virtual clock with frequency
111 1000000. It is used for most timekeeping in
119 etc... This is the clock that should normally be used
124 The i8254 clock. This is a real clock/timer with a nominal frequency of
125 1193182. It is divided down to give the scheduling clock. It isn't
126 available to applications.
128 The TSC clock (64-bit register) on fifth-generation or later x86 systems.
129 This is a real clock with a frequency that is equivalent to the number of
130 cycles per second of the CPU(s).
131 Its frequency can be found using the sysctl
132 .Sy machdep.tsc_freq .
133 It is used to interpolate between values of the scheduling clock.
134 It is only available to applications in a purely machine-dependent manner.
139 isn't 1000000 then the application is probably using the wrong clock.
151 This man page has been written by
153 after a description posted by