[unix-history] / contrib / xntpd / hints / linux


Requirements:	kernel 0.99.14 or newer, libc 4.5 or newer
------------

	With this configuration, xntp should build an run right out of the
box (see generic hints for how-to), with one big limitation: tickadj doesn't
work yet. This is especially painful since PCs are usually equipped with
untuned, badly-drifting quartzes, values up to 200 ppm being no exception.
Because the loop filter algorithms are limited to compensating no more than
100 ppm, currently only one workaround is possible:
	Compile your own kernel and adjust linux/include/linux/timex.h, 
line 67 (in pl14):

#define CLOCK_TICK_RATE 1193180 /* Underlying HZ */

	Since this is surely not true for your hardware, adjust the hundreds
to match your quartz. Adding 100 compensates for a drift of -83.8 ppm
(1/CLOCK_TICK_RATE). The number gets rounded to the nearest 100 so don't
bother to tune any finer.

Fixing tickadj is already in my work queue, so the previous comment should be
obsolete RSN. If you really need to run xntp on any earlier versions of the
kernel or libc, or have any other question not covered in the READMEs / hint
files (sorry, necessary comment in the Linux community ;-) feel free to ask
me (duwe@informatik.uni-erlangen.de)

xntp3.3b of 1993/12/06 : remember to change #define ntp_adjtime adjtimex to
__adjtimex in the Linux section (line 316). This is hopefully done if you
(don't :-) see this paragraph in the xntp3.x distribution.
Commit	Line	Data
98771864 GW	1
	2	Requirements: kernel 0.99.14 or newer, libc 4.5 or newer
	3	------------
	4
	5	With this configuration, xntp should build an run right out of the
	6	box (see generic hints for how-to), with one big limitation: tickadj doesn't
	7	work yet. This is especially painful since PCs are usually equipped with
	8	untuned, badly-drifting quartzes, values up to 200 ppm being no exception.
	9	Because the loop filter algorithms are limited to compensating no more than
	10	100 ppm, currently only one workaround is possible:
	11	Compile your own kernel and adjust linux/include/linux/timex.h,
	12	line 67 (in pl14):
	13
	14	#define CLOCK_TICK_RATE 1193180 /* Underlying HZ */
	15
	16	Since this is surely not true for your hardware, adjust the hundreds
	17	to match your quartz. Adding 100 compensates for a drift of -83.8 ppm
	18	(1/CLOCK_TICK_RATE). The number gets rounded to the nearest 100 so don't
	19	bother to tune any finer.
	20
	21	Fixing tickadj is already in my work queue, so the previous comment should be
	22	obsolete RSN. If you really need to run xntp on any earlier versions of the
	23	kernel or libc, or have any other question not covered in the READMEs / hint
	24	files (sorry, necessary comment in the Linux community ;-) feel free to ask
	25	me (duwe@informatik.uni-erlangen.de)
	26
	27	xntp3.3b of 1993/12/06 : remember to change #define ntp_adjtime adjtimex to
	28	__adjtimex in the Linux section (line 316). This is hopefully done if you
	29	(don't :-) see this paragraph in the xntp3.x distribution.