15 May
2016
15 May
'16
3:21 a.m.
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.