[ntp:questions] Re: Good GPS for attic?

David Schwartz davids at webmaster.com
Wed Feb 16 13:28:08 UTC 2005


"Maarten Wiltink" <maarten at kittensandcats.net> wrote in message 
news:42133d02$0$28978$e4fe514c at news.xs4all.nl...

> "David Schwartz" <davids at webmaster.com> wrote in message
> news:cuv9q1$pg1$1 at nntp.webmaster.com...

>> "John Pettitt" <jpp at cloudview.com> wrote in message
>> news:8F6Pd.6422$m31.77104 at typhoon.sonic.net...

>>> On my home net I set up GPS time because I wanted to see how cheaply
>>> I could do it ($350 emachines computer, $85 GPS18 LV, freebsd and
>>> about $5 of connectors).   I could have done it for under $120 with
>>> a used 486 box.
>>
>>     You need at least a Pentium because the '486 does not have a TSC
>> (instruction cycle counter). The TSC is absolutely essential to keeping
>> accurate time.

> That's not my experience. I have two, usually lightly loaded, 486 hosts
> with ancient to positively fossilised Linux versions and they run NTP
> really quite well. Unless I saturate my internet connection, I have
> offsets below 1ms nearly all of the time. One runs off my ISP's four
> peered NTP servers, the other off four pool servers.

    If you consider 1 millisecond to be sufficient, then sure.

> A Pentium running FreeBSD didn't do nearly so well.

    You would be wasting your money if you bought a GPS time receiver and 
settled for hardware whose accuracy was limited to around 1 millisecond. You 
should be in the low microseconds.

    DS





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