[ntp:questions] Re: Bought a GPS receiver--What next?
Richard B. Gilbert
rgilbert88 at comcast.net
Tue Nov 2 05:44:14 UTC 2004
Wolfgang S. Rupprecht wrote:
>> Worse, they quote a time accuracy of one microsecond. When I asked them,
>>"one microsecond between what and what?", they ignored me twice. Clearly,
>>it's one microsecond between GPS time and the clock's internal
>>representation of time -- to which you have no access.
>I always found that it was sad that the GPS interfaces didn't provide
>a simple 64-bit (or better yet 128-bit) cpu accessible register that
>simply provided the GPS's current internal time. The PPS output is a
>pretty cumbersome output to try to use.
>Does anyone have the ear of any of the GPS chip guys? Now that
>computer buses are turning into high-speed serial buses, would it be
>possible to design a low pin-count GPS chip that dropped into the
>PCI-e or hypertransport bus and just reported the current time in,
>say, nanoseconds (or better yet 2^-32 seconds) since the GPS epoch?
How would you transfer that 64bit time value? How would you control the
timeing of the transfer? Very few computers have 64bit parallel
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