Bug#743444: errors in the man page of adjtimex
Package: adjtimex
Version: 1.29-2.2
Severity: minor
There are errors in the man page of adjtimex. A research on
manpages.debian.org shows they are there since ages. For this bug I am
referring to the version we have in Wheezy: http://tinyurl.com/koxklkj
The section about the option -t says that one tick is roughly equivalent
to 100ppm (in the case illustrated). A bit below, the section about the
option -f says:
> -f newfreq, --frequency newfreq
> Set the system clock frequency offset to newfreq. newfreq can
> be negative or positive, and gives a much finer adjustment than
> the --tick switch. When USER_HZ=100, the value is scaled such
> that newfreq = 65536 speeds up the system clock by about 1 ppm,
> or .0864 sec/day. Thus, all of these are about the same:
> --tick 9995 --frequency 32768000
> --tick 10000 --frequency 6553600
> --tick 10001 --frequency 0
> --tick 10002 --frequency -6553600
> --tick 10005 --frequency -32768000
> To see the acceptable range for newfreq, use --print and look at
> "tolerance", or try an illegal value (e.g. --tick 0).
Now, the five cases are not equivalent.
The first is subtracting 500ppm with -t (9995-10000)x100ppm, and adding
500ppm with the frequency (65535x5)x100ppm. It is equivalent and
symmetric with the fifth case, where 5 ticks are added (=500ppm) and
500ppm are reduced via the frequency. Both result in a no change to the
clock speed (0ppm added/subtracted)
The second, third and fourth case are all equivalent, but they add
100ppm to the clock speed instead:
- the second keeps the ticks at 10000, but adds 65535x100 to the
frequency, so 100ppm
- the second adds one tick (100ppm), but sets the frequency at 0, so 100ppm
- the third adds two ticks (200ppm) but subtracts 65535x100 to the
frequency, so 100ppm; the total is again 100ppm
There are many ways to make the five cases equivalent, e.g.: either
change 1, 5 to match 2, 3, 4, or vice versa. I'll leave it to the author
of the man page to decide which change fits best.
Kind Regards
-- Marco
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