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I have some test equipment I am using to check the drift of some
oscillators. At the minute I am just evaluating the limits of the test
equipment. Ideally this should be in a temperature controlled
environment, but I don't have one. So I am thinking of doing one on the
cheap.

I'm wondering if I can use my Sun as a computer controlled heater, to
stabilise the temperature! Using as heating elements the 4 CPUs, and
adjusting the heat they produce by the amount of work they do, and/or
taking them offline. (I bet you have not known of an idiot trying that
one!!!)

Would taking the CPUs offline make them produce less heat or not? I know
when the Sun is doing a lot of CPU intensive stuff, it certainly runs
warmer.

Here's some data of room temperature (the first graph) where I purposely
induced large and rapid changes.

http://www.g8wrb.org.uk/useful-stuff...temp-data.html

If you look at the second graph, you will not the output from the test
equipment changed from about 99.8ns to 99.65ns (a change of 150ps) some
20 minutes into the test. Some 5.5 hours into the test I induced a large
temperature change, but the test equipment showed no sign of changing.
I'm not sure if its large changes, or large rate of changes that makes
the test equipment start giving poor results.

I'm wondering if I can get the Sun to do more/less work, to help
stabilise the temperature.

Hi David,

On Sat, 18 Jun 2005 20:52:30 +0100
Dave <nospam@nowhere.com> wrote:

> I'm wondering if I can use my Sun as a computer controlled heater, to
> stabilise the temperature! Using as heating elements the 4 CPUs, and
> adjusting the heat they produce by the amount of work they do, and/or
> taking them offline. (I bet you have not known of an idiot trying that
> one!!!)

You're like my son, always using things for purposes they were not
intended for. I'm trying to console myself with the idea he might be
the guy to solve the world's energy problems.

> Would taking the CPUs offline make them produce less heat or not? I know
> when the Sun is doing a lot of CPU intensive stuff, it certainly runs
> warmer.

Yes. CPUs use less power when they idle. To be absolutely sure, use
prtdiag to see if the temperature of the CPU drops when you take it
off line (do you get CPU temperature readings on a U80, on a Blade2000
it shows both the fan speed and the temperature of both CPUs).

> I'm wondering if I can get the Sun to do more/less work, to help
> stabilise the temperature.

You can parse the prtdiag output for the ambient temperature (which is
more or less related to the room temperature) and stop or start a few
CPU-intensive programs or take CPUs off-line as required.

$ prtdiag -v | grep Ambient
+em-board/cpu0 Ambient 27C -10C 0C 40C 60C okay
+em-board/cpu1 Ambient 26C -10C 0C 40C 60C okay

You'd need to write a little daemon to do the parsing and job/CPU
control as cron's resolution seems far too coarse (you care about
150ps, after all). pbind can be used to bind a process to a CPU,
allowing you to control which CPU is loaded.

Whether this would have any effect on the room temperature remains to
be seen, but it sounds like a fun way to waste some time if you've
got time to waste :-)

--
Stefaan
--
As complexity rises, precise statements lose meaning,
and meaningful statements lose precision. -- Lotfi Zadeh

Stefaan A Eeckels wrote:
> Hi David,
>
> On Sat, 18 Jun 2005 20:52:30 +0100
> Dave <nospam@nowhere.com> wrote:
>
>
>>I'm wondering if I can use my Sun as a computer controlled heater, to
>>stabilise the temperature! Using as heating elements the 4 CPUs, and
>>adjusting the heat they produce by the amount of work they do, and/or
>>taking them offline. (I bet you have not known of an idiot trying that
>>one!!!)
>
>
> You're like my son, always using things for purposes they were not
> intended for.

Very often that solves problems.

> I'm trying to console myself with the idea he might be
> the guy to solve the world's energy problems.

I think the word "Americans" is appropiate there, but I will comment no
futher.

>>Would taking the CPUs offline make them produce less heat or not? I know
>>when the Sun is doing a lot of CPU intensive stuff, it certainly runs
>>warmer.
>
>
> Yes. CPUs use less power when they idle. To be absolutely sure, use
> prtdiag to see if the temperature of the CPU drops when you take it
> off line (do you get CPU temperature readings on a U80, on a Blade2000
> it shows both the fan speed and the temperature of both CPUs).

I know they use less power when idle, but do they use less when taken
offline with psradm, than when online, but idle?

At the moment its inconvenient to locate my temperature sensor on the
output of the Sun's fans, but I'll get some longer leads on it and try.


>>I'm wondering if I can get the Sun to do more/less work, to help
>>stabilise the temperature.
>
>
> You can parse the prtdiag output for the ambient temperature (which is
> more or less related to the room temperature) and stop or start a few
> CPU-intensive programs or take CPUs off-line as required.
>
> $ prtdiag -v | grep Ambient
> +em-board/cpu0 Ambient 27C -10C 0C 40C 60C okay
> +em-board/cpu1 Ambient 26C -10C 0C 40C 60C okay

No such luck on the Ultra 80. However, I have can easily measure the
temperature. At the moment I have only one, but can add another 4, and
read them via the computer.

> You'd need to write a little daemon to do the parsing and job/CPU
> control as cron's resolution seems far too coarse (you care about
> 150ps, after all). pbind can be used to bind a process to a CPU,
> allowing you to control which CPU is loaded.

I care about less than 150ps actually, but that is of the time measured
by the instrument.

The errors induced in the test equipment will not occur with a change of
air inlet temperature that occur for 100's of ms or probably seconds.
Putting the CPUs on/offline will not cause rapid changes in room
temperature, so timing is not an issue.

Sorting out an algorithm might be.

> Whether this would have any effect on the room temperature remains to
> be seen, but it sounds like a fun way to waste some time if you've
> got time to waste :-)

Dave wrote:
>
> Stefaan A Eeckels wrote:
> > Hi David,
> >
> > On Sat, 18 Jun 2005 20:52:30 +0100
> > Dave <nospam@nowhere.com> wrote:
> >
> >

<snip>

>
> I think the word "Americans" is appropiate there, but I will comment no
> futher.

No such thing is appropriate! It's highly inappropriate, derogatory and
wildly OT, at best. I for one take great offense at the implication.

>
> >>Would taking the CPUs offline make them produce less heat or not? I know
> >>when the Sun is doing a lot of CPU intensive stuff, it certainly runs
> >>warmer.
> >
> >
> > Yes. CPUs use less power when they idle. To be absolutely sure, use
> > prtdiag to see if the temperature of the CPU drops when you take it
> > off line (do you get CPU temperature readings on a U80, on a Blade2000
> > it shows both the fan speed and the temperature of both CPUs).
>
> I know they use less power when idle, but do they use less when taken
> offline with psradm, than when online, but idle?

Check the SparcII operating specs for you procs on whatever the minimal
temperature is, that's probably close to the temp you'd see plus the
ambient heat given off by surrounding circuits. Cross-ref the hard-copy
or online handbooks for the Ultra-80 for other BTU related info.

Alternatively, measure the total BTU output and/or overall room
temperatures a few times with, and then without, the procs and any
additional systems online.

>
> At the moment its inconvenient to locate my temperature sensor on the
> output of the Sun's fans, but I'll get some longer leads on it and try.
>
> >>I'm wondering if I can get the Sun to do more/less work, to help
> >>stabilise the temperature.
> >
> >
> > You can parse the prtdiag output for the ambient temperature (which is
> > more or less related to the room temperature) and stop or start a few
> > CPU-intensive programs or take CPUs off-line as required.
> >
> > $ prtdiag -v | grep Ambient
> > +em-board/cpu0 Ambient 27C -10C 0C 40C 60C okay
> > +em-board/cpu1 Ambient 26C -10C 0C 40C 60C okay
>
> No such luck on the Ultra 80. However, I have can easily measure the
> temperature. At the moment I have only one, but can add another 4, and
> read them via the computer.
>
> > You'd need to write a little daemon to do the parsing and job/CPU
> > control as cron's resolution seems far too coarse (you care about
> > 150ps, after all). pbind can be used to bind a process to a CPU,
> > allowing you to control which CPU is loaded.
>
> I care about less than 150ps actually, but that is of the time measured
> by the instrument.
>
> The errors induced in the test equipment will not occur with a change of
> air inlet temperature that occur for 100's of ms or probably seconds.
> Putting the CPUs on/offline will not cause rapid changes in room
> temperature, so timing is not an issue.
>
> Sorting out an algorithm might be.
>
> > Whether this would have any effect on the room temperature remains to
> > be seen, but it sounds like a fun way to waste some time if you've
> > got time to waste :-)

The whole thing sounds a bit susceptible to the Heisenberg Principle in
a macro way Hope you have a descent oscillator in whatever's keeping
those ticks for you.

Ben wrote:
> Dave wrote:
>
>>Stefaan A Eeckels wrote:
>>
>>>Hi David,
>>>
>>>On Sat, 18 Jun 2005 20:52:30 +0100
>>>Dave <nospam@nowhere.com> wrote:
>>>
>>>
>
>
> <snip>
>
>>I think the word "Americans" is appropiate there, but I will comment no
>>futher.
>
>
> No such thing is appropriate! It's highly inappropriate, derogatory and
> wildly OT, at best. I for one take great offense at the implication.

I accept that. I should have perhaps said "America", since whilst as a
country the USA uses more energy per person (on average) than any other
country, that is not to say all Americans do.

>>The errors induced in the test equipment will not occur with a change of
>>air inlet temperature that occur for 100's of ms or probably seconds.
>>Putting the CPUs on/offline will not cause rapid changes in room
>>temperature, so timing is not an issue.
>>
>>Sorting out an algorithm might be.
>>
>>
>>>Whether this would have any effect on the room temperature remains to
>>>be seen, but it sounds like a fun way to waste some time if you've
>>>got time to waste :-)
>
>
> The whole thing sounds a bit susceptible to the Heisenberg Principle in
> a macro way Hope you have a descent oscillator in whatever's keeping
> those ticks for you.

Yes. One is an atomic oscillator (rubidium, I own), the other is an oven
controlled quartz locked to the 1 pulse per second ticks from a GPS
receiver. The device measuring, which is only measuring the *difference*
between the two atomic sources, does not have to be that accurate. Since
it only measures time differences. It's an HP 8370B time interval
counter, which is about the best affordable solution for this. It cost
over 20k $'s when new.