[time-nuts] Recommendations for NTP server

John Ackermann N8UR jra at febo.com
Fri May 5 14:35:54 EDT 2006

Glenn wrote:

>>>Is PPS kernel discipline compiled into the default FreeBSD kernel?
>>No, but it's a pretty easy thing to turn on -- you add a line to the
>>config file and tell it to go.  Pretty straightforward, *once* you find
>>the instructions.
> Where would I find these instructions?

It's in the FreeBSD users manual (or whatever it's called) which I found 
at the FreeBSD web site.  That gives general instructions for rebuilding 
the kernel.  I'm not sure if it specifically identifies the PPS flag or 
not.  On my 5.4 machine, it was adding:

# NTP PPS support
options         PPS_SYNC

to the /usr/src/sys/i386/config/PPS_KERNEL file, which was copied from 
the generic kernel config file.  Then rebuild, specifying PPS_KERNEL as 
the config file name.  There's also an associated .hints file which 
allows you to set the serial ports to low-latency mode by disabling the 
FIFO in the 16550 UART chip; this can reduce jitter.  I don't recall for 
sure, but I *think* it's setting the second bit (ie, 0x1_) in the flags 



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