[time-nuts] Msg to N.Z. time nuts

[Lux, James P]

On 5/19/09 1:15 PM, "Russell Rezaian" <rrezaian at motorola.com> wrote:

> At 12:58 PM -0700 2009/05/19, Hal Murray wrote:
>> USB has a bad reputation, but I think it's way way overblown.  Yes, it's
>> polled, but that polling is done in hardware and the time scale is 1 ms.  If
>> you are satisfied with an accuracy of a few 10s of ms, USB works fine.  The
>> problem is the GPS unit.
> 
> And I can confirm that for my very un-scientific experiments I do get
> a pretty consistent time sync around 1 MS plus or minus mark from a
> USB serial port adapter in best case conditions.  That's with no
> special work on a pretty stock consumer grade computer with an off
> the shelf USB to serial port.
> 

I would expect that the basic "frame" timing on USB (without actually
digging out my USB documents, because I'm lazy) is on the order of 125
microseconds (e.g. 8kHz, to support a 8ksps audio stream, just like IEEE1394
does), but that might just be a latency jitter bound.