In comp.unix.solaris Dave <someplace@nowhere-nice.com> wrote:
> I have a requirement where I need two Suns (both Netra T1s) to have
> their clocks close to each other during an experiment that lasts 4
> hours. During this time, neither Sun will have internet access and they
> will not be networked to each other.
>
> I suspect if I sync them by NTP before the experiment starts, then they
> will not drift by more than 500 ms over a 4 hour period. Does that seem
> reasonable? Has anyone actually ever made medium term (few hours)
> stability measurements of the clocks in Suns?

Can you simulate the conditions beforehand (with net access)? Run NTP,
get them all synced up. Enable logs and make sure you have driftfiles
in place.

On the client "disable ntp" in the config file so that polls are done,
but the clock is not modified. Let it run that way in simulated
conditions and see what your drift rate is.

Temperature will likely be the biggest factor in frequency changes.

If temperature is somewhat stable, 500ms should be achievable for a few
days.

--
Darren Dunham ddunham@taos.com
Senior Technical Consultant TAOS http://www.taos.com/
Got some Dr Pepper? San Francisco, CA bay area
< This line left intentionally blank to confuse you. >

Huge wrote:
> On 2008-03-20, Dave <someplace@nowhere-nice.com> wrote:
>> Huge wrote:
>>> On 2008-03-20, Dave <someplace@nowhere-nice.com> wrote:
>>>> Rex Mottram wrote:
>>>>
>>>>> Put the indoor machine in the refrigerator.
>>>>>
>>>>> RM
>>>> Unfortunately, that is not practical given the particular constraints I have
>>> Are the machines close enough together to connect a cable between them?
>>>
>>>
>> No - otherwise it would be easy with NTP over ethernet.
>
> Quite.
>
> So, how far apart are they?
>
The distance is not great - perhaps a few tens of metres, but it is
totally impossible to have any cables between the two locations.

In comp.unix.solaris Dave <someplace@nowhere-nice.com> wrote:
> The distance is not great - perhaps a few tens of metres, but it is
> totally impossible to have any cables between the two locations.

Is that limitation a physical one, or one dictated by EMI (?)
concerns? If the latter, are there any empty slots in the systems
into which you can put a gigabit (or 100BT) fibre card?

rick jones
--
web2.0 n, the dot.com reunion tour...
these opinions are mine, all mine; HP might not want them anyway...
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...

Rick Jones wrote:
> In comp.unix.solaris Dave <someplace@nowhere-nice.com> wrote:
>> The distance is not great - perhaps a few tens of metres, but it is
>> totally impossible to have any cables between the two locations.
>
> Is that limitation a physical one, or one dictated by EMI (?)

Both. Physically impossible, and even if it was, EMI would stop me doing
it.

On 2008-03-20 20:08:12 +0000, Dave <someplace@nowhere-nice.com> said:

> Rick Jones wrote:
>> In comp.unix.solaris Dave <someplace@nowhere-nice.com> wrote:
>>> The distance is not great - perhaps a few tens of metres, but it is
>>> totally impossible to have any cables between the two locations.
>>
>> Is that limitation a physical one, or one dictated by EMI (?)
>
> Both. Physically impossible, and even if it was, EMI would stop me doing it.

Would one of those Ethernet-over-power kits (eg Devolo) be any use? I
think both machines might have to be on the same circuit, but I'm not
certain about that.

Cheers,

Chris

Dave wrote:
> Huge wrote:
>> On 2008-03-20, Dave <someplace@nowhere-nice.com> wrote:
>>> Huge wrote:
>>>> On 2008-03-20, Dave <someplace@nowhere-nice.com> wrote:
>>>>> Rex Mottram wrote:
>>>>>
>>>>>> Put the indoor machine in the refrigerator.
>>>>>>
>>>>>> RM
>>>>> Unfortunately, that is not practical given the particular
>>>>> constraints I have
>>>> Are the machines close enough together to connect a cable between them?
>>>>
>>>>
>>> No - otherwise it would be easy with NTP over ethernet.
>>
>> Quite.
>>
>> So, how far apart are they?
>>
> The distance is not great - perhaps a few tens of metres, but it is
> totally impossible to have any cables between the two locations.
Wireless?

Or have I missed an earlier mention of it?

Cheers,
Gary B-)

--
__________________________________________________ ____________________________
Armful of chairs: Something some people would not know
whether you were up them with or not
- Barry Humphries

Chris Ridd wrote:

>> Both. Physically impossible, and even if it was, EMI would stop me
>> doing it.
>
> Would one of those Ethernet-over-power kits (eg Devolo) be any use? I
> think both machines might have to be on the same circuit, but I'm not
> certain about that.
>
> Cheers,
>
> Chris
>

No, not possible. The two systems, will each be on separate petrol or
diesel generators.

I think the most relieable way is for me to generate my own 1 pulse per
second from a rubidium oscillator. That can first be synced to GPS, then
once the pulses are appearing at the right time, the GPS will no longer
be needed. The oscillator I have is said to be ok as a stratum one unit
for 72 hours.

Gary R. Schmidt wrote:

>>> So, how far apart are they?
>>>
>> The distance is not great - perhaps a few tens of metres, but it is
>> totally impossible to have any cables between the two locations.
> Wireless?
>
> Or have I missed an earlier mention of it?
>
> Cheers,
> Gary B-)
>

No, you did not miss an earlier mention, but it is by no means certain
they will be in radio range, given one is in a pretty well RF shielded
enclosure. Exactly how well shielded is the whole point of the
experiment, but it might be too well shielded for a WiFi connection.

Dave wrote:
[SNIP]
>
> No, you did not miss an earlier mention, but it is by no means certain
> they will be in radio range, given one is in a pretty well RF shielded
> enclosure. Exactly how well shielded is the whole point of the
> experiment, but it might be too well shielded for a WiFi connection.
And, of course, running an Ethernet cable *through* the RFI shielding
will no doubt bugger it all up...

What about a LASER or LED modem-thingie? They used to exist, I can
recall reading up on them back in the 1980's, but I can't recall a
recent mention of them (but then, I haven't read a BlackBox catalogue
for yonks!).

Or simple optical fibre through the shielding to a router or summat.
(Okay, there goes 90% of teh budget... :-))

Cheers,
Gary B-)

--
__________________________________________________ ____________________________
Armful of chairs: Something some people would not know
whether you were up them with or not
- Barry Humphries

On 2008-03-20, Dave <someplace@nowhere-nice.com> wrote:
> Huge wrote:
>> On 2008-03-20, Dave <someplace@nowhere-nice.com> wrote:
>>> Huge wrote:
>>>> On 2008-03-20, Dave <someplace@nowhere-nice.com> wrote:
>>>>> Rex Mottram wrote:
>>>>>
>>>>>> Put the indoor machine in the refrigerator.
>>>>>>
>>>>>> RM
>>>>> Unfortunately, that is not practical given the particular constraints I have
>>>> Are the machines close enough together to connect a cable between them?
>>>>
>>>>
>>> No - otherwise it would be easy with NTP over ethernet.
>>
>> Quite.
>>
>> So, how far apart are they?
>>
> The distance is not great - perhaps a few tens of metres, but it is
> totally impossible to have any cables between the two locations.

Is this one of those interview questions which has no answer?

)

--
"Be thankful that you have a life, and forsake your vain
and presumptuous desire for a second one."
[email me at huge {at} huge (dot) org <dot> uk]