[time-nuts] Set time on Solaris computer from HP 58503A

Hal Murray hmurray at megapathdsl.net
Sun Dec 14 16:26:58 EST 2014

gigneil at gmail.com said:
> Based on my recent testing - including Solaris - you will be better off with
> the Internet unless your USB adapter is far better behaved than the several
> I have here 

That depends,  (TM)

How good/bad is your network connection?  Mine gets over 3 seconds of queuing 
delays.  I challenge anybody to find a USB device that bad.

There are only 2 or 3 significant vendors of USB-serial chips.  I think they 
are reasonably well supported by all major OSes.

USB is polled, so interrupt latency turns into polling latency.  I think the 
polling cycle is 1 ms for slow things like serial ports.  Maybe 1/4 ms for 
faster things like disks.  At the system level, faster polling means more 
overhead and slower polling means bigger buffers.

Many of the low cost GPS units use the SiRF chips.  They have a wander of 
~100 ms.  I said wander rather than jitter because it's very slow as in 
hours.  You can't filter it out with a 10 or 100 second sample.

The old Garmin GPS-18-USB (not 18x) units had pretty good timing.  No wander. 
 Unfortunately, they weren't very sensitive.

These are my opinions.  I hate spam.

More information about the time-nuts mailing list