[time-nuts] Selecting server hardware (newbie question)

[Poul-Henning Kamp]

In message <20060128092400.42708BDE0 at ip-64-139-1-69.sjc.megapath.net>, Hal Murr
ay writes:
>
>> I am trying to select a host machine for a dedicated NTP server.  I
>> have  several spare PCs to hand, with processor speeds around 500 MHz
>> - all my  budget will allow for the moment. 
>
>You will probably get more/better responses from comp.protocols.time.ntp on 
>usenet.
>
>My 2 cents...

Another 2 cents:

>As a sanity check, several people use the Soekris Engineering net4501 as a 
>NTP server.
>  http://www.soekris.com/net4501.htm
>It's got a 133 Mhz 486 class processor.  (Runs cool.)

The 4501 is actually particularly good if you use the onboard
timers to timestamp your 1PPS signals:
	http://phk.freebsd.dk/soekris/pps/

I know of no other computer that can do this out of the box.

>The main source of instability is the temperature of the crystal.

Agreed.  Replacing the 33 MHz xtal with something better is highly
advised.

>Most systems use the 32 KHz battery backed TOY (Time-of-Year) clock for 
>timekeeping rather than the CPU crystal. 

Wrong, few systems do.   Most systems use the 32.768 kHz xtal to run
their battery-backed Real Time Clock, but this is only consulted on
boot to get an initial fix on time.

>This is good because it's generally 
>farther from the heat generating CPU than the CPU crystal.

This has no hold in reality.

>For software, the PPS support needed by GPS clocks (and others)
>is part of the normal source code for some OSes.  It's not on Linux
>but is available as an add-on.  I suggest using whatever you are
>most comfortable/familiar with.

I'm obviously biased, but I think the FreeBSD code I wrote is an
order of magnitude ahead of anything else:

	http://phk.freebsd.dk/pubs/timecounter.pdf

Summary:

A Soekris NET4501, a bit of work with a soldering iron, an OCXO possibly
with a PLL to generate something roughly 33MHz and a GPS receiver
will get you about as good a NTP server as money can buy and at a
rock bottom price.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.