On Nov 1, 2013, at 2:04 PM, Mouse <mo...@rodents-montreal.org> wrote:
> ... > But it still may not work in the sense of living up to the expectations > people have come to have for PPS on serial ports. > > My worry is not that it's not the best time available in some > circumstances. My worry is that putting it into the tree will lead to > its getting used as if it were as good as PPS on anything else, leading > both to timeservers that claim stratum 1 but give bad chime and to > people blaming NetBSD for its crappy PPS support when the real problem > is that they don't understand the USB issues and it _looks_ like any > other PPS support until you test the resulting time carefully. Not just PPS on serial ports, but PPS on other hardware. I don't know this API. But my first reaction when I saw the designation "PPS" is to think of GPS timekeeping boxes and other precision frequency sources that have a PPS output. On those devices, the PPS output is divided down from the main oscillator frequency, i.e., you can expect accuracies of 10^-9 for modest price crystal oscillators, 10^-10 to 10^-12 for higher end stuff -- and jitter in the nanosecond range or better. It seems rather confusing to have another interface that goes by the same name but has specs 6 or more orders of magnitude worse. How about a different name that avoids this confusion? paul