[time-nuts] Re: Ryzen mobos with serial port for Garmin GPS?

[Rich Wales]

For what it may be worth, here are the current clock performance 
measurements for the two stratum-1 time references on my home LAN. Each 
computer has an AMD FX-8350 processor on an ASUS motherboard, with a DB9 
serial header on the motherboard, and each system has a Garmin 18x 
receiver wired to a DB9 serial connector.

The jitter (dispersion) in each case seems to be significantly less than 
what I might expect from a USB-based connection.  I don't have specifics 
anymore, but I remember I tried connecting a Garmin 18x GPS to a PCIe 
serial card once, and the result was way too unstable to provide any 
sort of useful time reference.  I assume this was because the PCIe 
serial card was really just a serial interface to a USB chip, right?

Note that I'm using *chrony* here (not *ntp* or *ntpsec*).

(11/05 12:27:04 richw at equality ~ 2118) $ chronyc tracking
Reference IDÂ Â Â  : 47505053 (GPPS)
Stratum         : 1
Ref time (UTC)Â  : Fri Nov 05 19:26:59 2021
System time     : 0.000001197 seconds slow of NTP time
Last offset     : -0.000000044 seconds
RMS offset      : 0.000001942 seconds
Frequency       : 8.615 ppm slow
Residual freq   : -0.000 ppm
Skew            : 0.052 ppm
Root delay      : 0.000000001 seconds
Root dispersion : 0.000030960 seconds
Update interval : 16.0 seconds
Leap status     : Normal
(11/05 12:27:10 richw at equality ~ 2119) $

(11/05 12:27:39 richw at memoryalpha ~ 2000) $ chronyc tracking
Reference IDÂ Â Â  : 47505053 (GPPS)
Stratum         : 1
Ref time (UTC)Â  : Fri Nov 05 19:27:25 2021
System time     : 0.000005428 seconds slow of NTP time
Last offset     : -0.000024016 seconds
RMS offset      : 0.000031762 seconds
Frequency       : 30.816 ppm slow
Residual freq   : -0.025 ppm
Skew            : 1.607 ppm
Root delay      : 0.000000001 seconds
Root dispersion : 0.000054530 seconds
Update interval : 16.0 seconds
Leap status     : Normal
(11/05 12:27:43 richw at memoryalpha ~ 2001) $

*Rich Wales*
richw at richw.org