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

[Hal Murray]

> 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...

There are several issues.  The main ones are hardware and software.

Almost any old PC will make a reasonable NTP server.  But how good do you 
want?  (This the time-nuts mailing list.  You might want real good.)

The speed of the CPU is not a major issue.  It roughly cancels out: delays on 
the receive path are compensated by similar delays on the transmit path.

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 main source of instability is the temperature of the crystal.  NB: Self 
heating is significant.  My mostly idle systems show conspicuous glitches at 
4AM when the cron jobs fire off.  Aside from that, they easily track the 
daily temperature changes in my house.  My main system has lots of noise when 
I'm doing things.

It's not hard to use an NTP server to measure temperature.
  http://www.megapathdsl.net/~hmurray/ntp/slope.gif
  http://www.ijs.si/time/temp-compensation/

Most systems use the 32 KHz battery backed TOY (Time-of-Year) clock for 
timekeeping rather than the CPU crystal.  This is good because it's generally 
farther from the heat generating CPU than the CPU crystal.



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.

If you don't have a GPS gizmo already, the Garmin GPS 18-LVC seems to be the current best-buy.  It's under $100.  Mine works well.  I got it from Provantage.  I don't know anything about UK availability.



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