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[time-freq] Linux PPS and FreeBSD issues

Jeff Mock jeff at mock.com
Fri Dec 28 19:27:07 UTC 2007

John described the situation precisely.  It's been a sad state of 
affairs for many years.  I did a contract project several years ago that 
needed good PPS timing source to solve a problem serving long running 
MPEG-2 streams.  I wound up paying to get PPSkit updated to PPSkit-2.1.2 
in hopes of making the code part of the official kernel releases.

We solved our immediate PPS problem, but never got anyone interested in 
making the PPSkit code part of the regular kernel release. It doesn't 
seem to be a technical issue, there really is some bad chemistry going 
on with PPS support and the kernel people.


John Ackermann N8UR wrote:
> Hi Gregg --
> I'm by inclination a Linux guy, but unfortunately there is some sort of
> bad juju between the kernel people and the NTP people, and as a result
> getting decent PPS timekeeping out of Linux is an ongoing challenge.  I
> run FreeBSD (actually, the CF-based nanoBSD version) on my Soekris
> servers as that seems to be the best way to make things work.
> There is a shared memory (shm) program called shmpps that can pick up a
> PPS signal from a serial port and pipe it to NTP, but I've had trouble
> keeping that going for long uptimes.
> It's a shame that Linux seems, for reasons I don't understand, to be
> unable/unwilling to have the necessary kernel stuff to avoid patches,
> but it's been that way for years and I haven't seen any sign of changes...
> John
> ----
> Gregg Levine said the following on 12/27/2007 06:43 PM:
>> Hello!
>> I've been sorting through and reading messages on news://comp.protocols.ntp .
>> It seems to be an interesting study. There is a group there (or it
>> seems to me to be one.) that prefers FreeBSD exclusively. And there
>> are people like myself who are concerned with the PPS inclusion into
>> the Linux kernel. Accordingly there are kits available for this on the
>> Kernel.org server. But only for and for The author
>> of the kit is interested in updating this, but he's not clear on when
>> it would be released for the later 2.6 ones.
>> There is even one fellow who has NTP running on his Sun box from the
>> same time period as the I486DX2, he's got it running rather nicely.
>> But the big question for me is simply running Linux on hardware from
>> the same time period, and naturally that's what I've been up to.
>> The last I time I investigated FreeBSD was during the ramp up to
>> version 4.0. I daresay I never got things to work properly then. I've
>> heard some interesting complaints about building a kernel for that
>> operating system, versus the others from the BSD family, and Linux.
>> Would anyone care to comment?
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