[ntp:questions] ntp server specs

David J Taylor david-taylor at blueyonder.co.uk.invalid
Wed Jun 15 19:05:42 UTC 2011

"E-Mail Sent to this address will be added to the BlackLists" 
<Null at BlackList.Anitech-Systems.invalid> wrote in message 
news:itauip$4v0$1 at dont-email.me...
> David J Taylor wrote:
>> "C BlacK" <rblak at non.net> wrote in message
>>> For our discussion, lets say there are many machine
>>> but the distance is not going to me more that 100ft.
>> Then some top-of-the head sums might be:
>> 100 machines - RS-232 input resistance, guess, 4K,
>>  all 100 in parallel 40 ohms.
> A 5v PPS signal with more than 125ma drive?
> Not likely from a normal TTL chip.

No, you would need a suitable specified line driver, of course.  A couple 
of transistors might do the job.

> 100 PC RS232 serial ports tied together,
> fed from one PPS driver?
> I'd think you would have a lot of stray ground currents
>  running around.
>  Even if they were isolated RS422/485 receivers,
>   100 in parallel, fed from one PPS driver,
>   seems like it would be problem prone.

Which is why I suggested checking the waveforms.  "many machines and not 
more than 100 feet" is quite vague.  It could be that 10 groups of ten 
(were it 100 PCs) might be better.

How many PCs could be connected to a thin-wire Ethernet segment?  Perhaps 
30 in the 185m limit?  That was working at 10Mb/s.  Might be a guide as to 
what to aim for.


More information about the questions mailing list