[rescue] NTP and Fuzzballs, was Re: Linux wet paint, was Re: Spark10 CPU question (must fix - SPARC damnit :-) )

Dave McGuire mcguire at neurotica.com
Fri Dec 23 19:27:29 CST 2016

On 12/23/2016 05:52 PM, Carl R. Friend wrote:
>>   Yes.  But my desktop doesn't sync to my GPS receiver, it syncs to the
>> computer that's wrapped around it. ;)  (Datum Tymserve 2100)
>    My stratum-1 can be used as a desktop if I fire up an X-terminal
> or other display system for it.  I wanted to "do things the hard
> way" when I set the thing up and actually paid a premium for a box
> that had a BNC nozzle for the antenna, an RS-232 nozzle to talk to
> the computer, and a power jack.  So, that's the stratum-0 device,
> and it's in a separate box.

  Yes, but you can't set up an NTP on another machine on the network to
peer with a 4800 baud NMEA-protocol serial device. ;)  Technically, the
computer is treating the stratum-0 device (GPS receiver) as a server, as
you no doubt know.

> (Likely your "appliance" uses something entirely similar "under the covers".)

  Yes, it's an embedded system based on (IIRC) a 68HC11, with an OCXO
that's phase-locked to the 1PPS output from an embedded GPS receiver
module, providing a disciplined 10MHz output, and an NTP service that
uses the GPS receiver's NMEA output.

  Interestingly, it also outputs IRIG-B time code, which is handy.

>    The device it's attached to is an old Pentium Pro motherboard
> living in an older Gateway 2000 box.  The interrupt chain is simple
> enough so the thing doesn't jitter too much and the long-term
> offset averages in the 25 nS range.  Newer systems will do worse
> because of the convoluted interrupt architecture and don't stand
> a chance with USB <-> RS-232 converters.

  Yes.  Many systems' clocks are awfully behaved. :-(

> [CRF]>    At some point, I really want to try lighting up a fuzzball.
>>   Me too!  Let me know if you decide to finally get to that; maybe we
>> could do it collaboratively.
>    I've got period-appropriate iron that runs, so that's a no-brainer.
> It's the time to actually execute.

  Same here, on both counts.

> Also, the version of NTP that'd
> run on the fuzzball would not understand a GPS receiver without a
> massive rewrite and I'm no longer up to doing a WWV clock, nor do I
> have access to space for a proper antenna.

  Well I can do that part. :)

>>   (that's on-topic!)
>    These things sometimes happen.  I need to revisit the fuzzball
> idea at some point.  I really do.

  Same here!  Let me know.


Dave McGuire, AK4HZ
New Kensington, PA

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