Bruce Simpson <b...@fastmail.net>: > On 13/05/16 20:39, Eric S. Raymond wrote: > >In 2012, nearly three years before being recruited for NTPsec, I > >solved this problem as part of my work on GPSD. The key to this > >solution is an obscure feature of USB, and a one-wire > >patch to the bog-standard design for generic USB that exploits > >it. Technical details on request, but what it comes down to is > >that with this one weird trick(!) you can mass-produce primary time > >sources with a jitter bounded by the USB polling interval for > >about $20 a pop. > > > >The USB 1 polling interval is 1ms. > > What about USB 3.1 (assuming the device is not intended to be backwards > compatible with the polling model) ? I should point out Intel intend to > retire EHCI/UHCI and implement only xHCI.
Nobody makes GPSes with even USB 2 or 3 yet, and it is unlikely to happen for a long time. Cost reasons - USB GPSes are cheap consumer-grade hardware and the manufacturers care about fractions of a cent on the BOM. -- <a href="http://www.catb.org/~esr/">Eric S. Raymond</a>