Re: Slightly OT: Looking for good GPS PCI time sources

Perry E. Metzger wrote:
I'm building a system for a client to measure network latencies in a
distributed system very accurately -- microsecond accuracy is desired
(though I suspect in practice we'll end up doing a bit worse). To do
this, I need to get high quality clock sources for the machines doing
the measurement. One obvious choice would be PCI cards that
synchronize to GPS.

I figure if any group has significant experience with such devices,
this one would -- anyone have any recommendations? Also, can anyone
think of another reasonable way to get this sort of accuracy on stock
PC hardware?

One consideration might be whether the cards in question allow readout
of the time as a single atomic operation -- if they don't, one can't
(for example) read the time without worrying about locking...

Perry

PCI cards that synchronize to GPS are available. Meinberg Funkuhren sells one such. Another is the BC637PCI from Symmetricomm. They are rather expensive; the Meinberg card sells for over $1000 US. I don't know what list price for the BC637 is but I saw a used one sold for over $400 US on e-Bay a few years ago. I believe that both of these cards feature a GPS disciplined OCXO, at least as an option. If you buy one and get tired of it, all donations are gratefully accepted! :-)

There is one GPS receiver, whose brand name I have forgotten, that will give you the time stamp for the leading edge of a pulse you supply. The name "Palisade" just bubbled up from the sludge at the bottom of my mind. http://www.leapsecond.com/museum/palisade/ It does this trick via a serial port so you can forget about time stamping two pulses a few microseconds, or even milliseconds apart.

.

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