[ntp:questions] Windows time question.
David J Taylor
david-taylor at blueyonder.co.uk.invalid
Wed May 4 05:54:44 UTC 2011
"unruh" <unruh at wormhole.physics.ubc.ca> wrote in message
news:slrnis0nra.4on.unruh at wormhole.physics.ubc.ca...
> Unfortunately , AFAIK, usb is terrible for delivering a PPS-- ie no
> interrupt lines-- the problem with having only two data lines (one beign
> signal ground)
USB is not as good as a direct connection, but it is not "terrible" - see
my tests here:
PPS delivered over a serial-USB convertor which carries the DCD line shows
significantly better performance than syncing over a LAN connection to a
stratum-1 server. Jitter was around 45 microseconds with the PPS over
USB, and about 160 microseconds when LAN synced. It could be that the
faster polling with the PPS source also helped reduce the jitter. PPS
over USB is likely to be significantly better than a WAN sync as well.
Although I have a GPS on a USB stick, it's a logging device and I don't
think that it supplies a NMEA feed. Perhaps I could test this later this
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