[ntp:questions] Re: PCI add on oscillator

Greg Dowd GDowd at symmetricom.com
Mon May 9 20:16:27 UTC 2005

Look at the refclock driver list.  There are many add-in cards from
Meinberg, Symmetricom and others which are supported by refclock
drivers.  These cards typically include a voltage-controlled crystal
oscillator and dac control circuit to provide much better stability than
your standard xtal as well a stratum 1 functionality with an attached
reference source (gps, irig, etc).  But, it's all relative.  Ntpd does
pretty well with drift compensation on a well-soaked box for short
intervals.  How long to do you need to flywheel?  

Many of the add-in cards have ovenized crystal options.  If you move
into Vxi or VME space, you can even go atomic with Rubidium.  If you
have the money, we can even provide a hydrogen maser.  Unfortunately, it
won't fit in a pci slot.

If you want to go the other way, you might be able to tack in a
replacement RTC on your mboard.  I think Dallas has a drop-in rtc with a
temperature compensated crystal.

Message: 3
Date: 09 May 2005 14:42:38 +0200
From: Ulrich Windl <Ulrich.Windl at RZ.Uni-Regensburg.DE>
Subject: [ntp:questions] Re: PCI add on oscillator
To: questions at lists.ntp.isc.org
Message-ID: <86r7ggmuyp.fsf at pc8032.rz.uni-regensburg.de>
Content-Type: text/plain; charset=us-ascii

Maybe ask the people at Meinberg; clocks are their business:


"Joshua Coombs" <jcoombs at gwi.net> writes:

> Given standard pc clocks are less than ideal, with wide drift, etc, 
> does anyone make a good quality oscillator as an add in, say via PCI? 
> Ideally something NTP could discipline, so one could build a PC that 
> could serve reliable time for more than 5 mins if external time 
> sources became unavailable.  I believe I read an article by PHK where 
> he built one for test purposes, the discussion of 500ns accuracy got
me thinking about it again.
> Joshua Coombs

Greg Dowd
gdowd at symmetricom dot com (antispam format)
Technologist, TT&M Div.
Symmetricom, Inc. 

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