overheating help

  • Thread starter Thread starter Steven Campbell
  • Start date Start date
It is irrelevant whether fan blows or sucks. Air flow
quantity - the CFM - determines temperature of internal
chassis. Obviously internal temperature will be slightly
cooler at intake than at exhaust. But when discussing CPU
cooling, then even that difference is irrelevant.

1) Virtually all chassis air recycles everywhere before it
is finally removed - no matter whether fan blows or sucks.
Over time, internal termperatures will stabilize to the point
that that CFM equation defines. Nothing overheats as
speculated - without numbers. Temperatures climb to and
remain at temperatures defined by that simple stability
equation. Again, you really need to first learn the basic
science before speculating. Everywhere that air moves inside
the chassis will stabilize to a temperature well below what a
CPU heatsink requires.

2) If a system has heat problems in a 70 degree F room, then
how will it every function in a 100 degree room. Every
properly constructed system works just fine when operating in
a 100 degree room. That means in a 70 degree room, internal
chassis temperatures are nothing - trivial. Just another
reason why more fans will not significantly effect that 70
degree C temperature spike.

3) The equations say a single 80 mm chassis fan is more that
sufficient cooling for most any system. Then we add
additional cooling through metallic chassis. What was more
than sufficient cooling is now that much more than sufficient
cooling. But another reason why more chassis fans provides
nothing.

Three times over, more fans solve nothing for the OP. Too
much time wasted on speculation irrelevant to the OP's CPU
temperature spike. Would adding six more fans solve his 70
degree temperature spike? Of course not. Again, one fan or
seven chassis fans is not going to solve this problem
especially since one fan alone is more than sufficient. Even
simple multiplication, given a fan's CFM, makes that obvious.

Fan placement did make a difference when no Pentium II or III
CPU required a CPU fan. Airflow is essential to how a
heatsink operates - again more fundamental concepts. Now that
CPU heatsinks have cooling fans moving air often many times in
excess, the location of a chassis fan make no difference.
Blowing or sucking chassis fan also makes no difference.
Internal chassis temperature is simply a function of intake
air temperature and fan's CFM.

But let's do this. If so certain that temperatures vary
that much inside the case, then provide those numbers.
Please demonstrate this radical temperature difference at
either end of a motherboard. Please show us where chassis
temperature can drop 15 degrees F simply by reversing a fan.
Please show how fan placement can result in tens of degrees C
temperature difference. If placement of a fan blowing or
sucking made a significant difference, then provide numbers
you had before posting. What are those numbers?
 
Run a basic system without chassic fan. IOW remove power
supply and monitor temperature of a system run in a 70 degree
room with only the metal chassis for cooling. IOW get
numbers. System still works just fine. Plenty of cooling
just from metal chassis. But again, the system must also work
in a 100 degree room. Therefore one chassis fan is
necessary. Same one fan that cools power supply heatsinks
also removes sufficient air from inside most chassis... so
that computer can also work in a 100 degree F room.

One who disputes this has two choices. Either provide the
calculations that say otherwise OR perform an experiment and
report back numbers - temperature and power consumption.
Either way, the one thing constantly missing from this
'chassis solution' are numbers.

Kevin. If cutting holes is so advantageous, then show us -
with numbers. How many degrees less is temperature inside a
chassis with that bigger hole? Prove your point. Provide
numbers. Show us how bigger cooling holes will stop a 70
degree C spike in his CPU. Where are the numbers?

In the meantime, Kevin's solutions are totally irrelevant to
the OP's problem - a 70 degree C spike in CPU temperature.
 
| Run a basic system without chassic fan. IOW remove power
| supply and monitor temperature of a system run in a 70 degree
| room with only the metal chassis for cooling. IOW get
| numbers. System still works just fine. Plenty of cooling
| just from metal chassis. But again, the system must also work
| in a 100 degree room. Therefore one chassis fan is
| necessary. Same one fan that cools power supply heatsinks
| also removes sufficient air from inside most chassis... so
| that computer can also work in a 100 degree F room.
|
| One who disputes this has two choices. Either provide the
| calculations that say otherwise OR perform an experiment and
| report back numbers - temperature and power consumption.
| Either way, the one thing constantly missing from this
| 'chassis solution' are numbers.
|
| Kevin. If cutting holes is so advantageous, then show us -
| with numbers. How many degrees less is temperature inside a
| chassis with that bigger hole? Prove your point. Provide
| numbers. Show us how bigger cooling holes will stop a 70
| degree C spike in his CPU. Where are the numbers?
|
| In the meantime, Kevin's solutions are totally irrelevant to
| the OP's problem - a 70 degree C spike in CPU temperature.

Sorry, W_tom, but I refuse to engage in a 'flame war' with you.
All of my comments are based on experience, while you appear to be working
on theory.
I have tried running a system without chassis fans before, a 1.0 GHz
Athlon Thunderbird on Gigabyte motherboard with the AMD Irongate chipset. In
a large closed PC case, temperatures rose steadily and I must confess that I
'chickened out' with the CPU appraoching 80 and the m/board chip at 65. Run
uncased, allowing convection currents in a relatively cool room to help, the
same hardware is just about okay at 65 CPU and 55 m/board.
I still maintain that using an intake fan, so that clean air is brought
into the case through a filter, is far better than dragging dust and dirt in
through the various holes in a typical PC case. Giving the air a relatively
clean passage to and from the fan results in less noise ('roar') from
turbulance. I will endeavour to find some way of measuring this over the
next few days, record the results and document accordingly.
BTW: My first suggestions to the OP were that they carefully check the
mounting of the existing HSF (including the thermal interface) and ensure
that it is clean and not lagged by a jacket of dust. I also covered making
sure that nothing, such as a ribbon cables, was obstructing the HSF airflow.
Have you read the entire thread ? I felt we had got past HSF issues and
were now considering other factors, such as the flow of air through the PC
case.
Kevin.
 
Maintain all you want. Without learning basic theory, your
experience could teach you nothing. You are being made the
poster child of an 'experienced user' who forgot how to learn
and therefore promotes myths. Myths that do not address the
OPs original problem.

You are working only from what you 'feel'; facts such as
numbers be damned. You could not even post the incoming and
outgoing temperatures - because to do so would have exposed
the error in your 'feelings'. You are confronting fundamental
science, tempered by decades of experience by using hearsay
speculation. But again, your posts don't address the OP's
original problem; a CPU temperature that may spike to 70
degree C. One fan or seven still would not address his 70
degree C problem - obviously. Please feel free to maintain
the 'poster child' reasoning. It demonstrates why experience
alone - no underlying theory - is only speculation. "I did
this, that happened, but I don't know why" is what you have
posted.
 
Kevin Lawton said:
Oh no it isn't !
Quite often case grills are just a few concentric circles of
small holes. Their total area might amount to less than two
square inches. An three-inch fan has an area of around six
square inches, and axial fans an't deliver much pressure.
The net result is that the little holes will both reduce
airflow by increasing air resistance and crate turbulence.
Click to expand...
1) Try running a case fan in free air without a grille.
Notice how quite it is.
Click to expand...

You are absolutely correct that it's quite -- quite quite, in fact.
2) Try blowing with your mouth into free air, and then
at or through an empty PC case fan grille. Notice how much
noise the air makes as it impinges on grille. Notice also
how not all of the air you are blowing passes through
the grille, but bounces off the metal instead.
Click to expand...

It's good that you're not one of those people who obsesses about
cooling for the sake of cooling and who performs proper systematic
testing and doesn't use ad hoc methods that are subject to great bias.
 
Re overheating: I haven't read this entire thread, and hope I'm not
repeating something that's been said.

The problem can be due to badly located ventilation, rather than lack of
fan power. I used to have overheating problems with Cyrix 200MHz-
equivalent processors (which tended to overheat) in cases with lots of
holes in the back. The air flowed through the holes, and straight out
via the power-supply fan without a sniff at the processor. Overheating
problems were cured by blocking up these "cooling" holes.
 
w_tom wrote:
Snip
Fan placement did make a difference when no Pentium II or III
CPU required a CPU fan. Airflow is essential to how a
heatsink operates - again more fundamental concepts. Now that
CPU heatsinks have cooling fans moving air often many times in
excess, the location of a chassis fan make no difference.
Blowing or sucking chassis fan also makes no difference.
Internal chassis temperature is simply a function of intake
air temperature and fan's CFM.
Click to expand...

And there is the contradictiion :)
Are you seriously suggesting that irrespective of the position and
direction of the chassis fan, it will see the same intake temperature in
a "real world" situation?

Doesn't your mathematical model have walls, central heating radiators,
and temperature gradients?
Or are we to assume that your model requires the PC to be standing on a
table in an air conditioned room with 2m clearance all around it? :)

Lee
 
| w_tom wrote:
| Snip
|
|| Fan placement did make a difference when no Pentium II or III
|| CPU required a CPU fan. Airflow is essential to how a
|| heatsink operates - again more fundamental concepts. Now that
|| CPU heatsinks have cooling fans moving air often many times in
|| excess, the location of a chassis fan make no difference.
|| Blowing or sucking chassis fan also makes no difference.
|| Internal chassis temperature is simply a function of intake
|| air temperature and fan's CFM.
||
|
| And there is the contradictiion :)
| Are you seriously suggesting that irrespective of the position and
| direction of the chassis fan, it will see the same intake temperature
| in a "real world" situation?
|
| Doesn't your mathematical model have walls, central heating radiators,
| and temperature gradients?
| Or are we to assume that your model requires the PC to be standing on
| a table in an air conditioned room with 2m clearance all around it? :)

To be honest, and to try to de-fuse points of argument, I think we have
just about all agreed on two points:
1) Provided you get some sort of air flow through the PC case, however it
occurs, then under most normal or typical situations the HSF on the CPU
should be able to do the job adequately provided it is properly mounted. AMD
have already determined the required specifications and (hopefully) the
manufacturer of the HSF has met or exceeded them.
2) A build-up of fluff / dust / dirt on the CPU heat-sink and around the
fan is likely to impair the cooling efficiency to some degree, and the same
build-up within the PSU will impair cooling to some extent also. Whatever
the figures pan-out to be, we can agree that this dust build-up is better
avoided if at all possible.
If anyone actually disagrees with the above two statements, then please
say so.
From the above does it not then seem reasonable that it would be
preferable to draw clean cool air into the PC case through an air filter,
rather than let it be randomly sucked in through all the various gaps and
holes - complete with a load of airbourne dust and dirt ?
Okay, I do not have exact measurements of exactly how many CFM flowing
through a certain size filter will prevent what thickness of dust build-up
over how long a time. Is precise measurement of this actually necessary for
the above principle to be valid ?
If we are using a fan which we know is rated at 6 cfm and measure the PC
case to find it is, say, 3 cubic feet then we would expect the air in the
case to change twice per minute. If we know that the air temperature inside
the PC case is 25 degrees celsius, the thermal rsistance of our chosen HSF
is 0.5 degrees celsius per watt, and the dissipation of the CPU is 60 watts,
then we can calculate that the CPU temperature will be maintained around 55
degrees celsius. Where does this get us ? Well, we can see that we require
sufficient airflow thorugh the PC case to prevent the temperature inside
rising further due to the dissipated heat, we need the thermal efficiency of
the HSF to be maintained and not become reduced for any reason such as dust
or dirt, and we can see that an increase in CPU dissipation could lead to a
rise in temperature. The figures did not change what we can surmise from
experience and common-sense.
Back to the OP's problem: the CPU is showing 70 degrees, and three
different HSFs have been tried - two of them known to be good-quality makes.
These have been installed carefully and thermal compound has been used. The
choice and correct mounting of the HSF has already been well discussed in
this thread.
Unless I am missing something (please say so if I am) then that leaves us
with two variables - the dissipation of the CPU and the airflow. The heat
dissipation of the CPU can be increased by running CPU-intensive tasks or by
over-clocking. This has also been covered in this thread.
We know that the PC in question is sitting in the corner of a room and air
flow to and from the outside of the case might not be optimal. We know that
reversing the case fan changes the balance of measured/observed
temperatures - one way the CPU runs hot and the m/board is okay, the other
way the CPU is cooler but the m/board runs hotter.
Given that we are remote from the PC in question, but are trying to help,
we have to get there in stages. These stages involve suggesting things for
the OP to try and observations for the OP to make and report back.
The current area of discussion is that of airflow and dust build-up.
With the above in mind I would like to try to make some progress by asking
the OP two things.
1) Please inspect the interior of the PC for a build-up of dust and dirt,
especially around fans and heatsinks - in between cooling fins - and report
back. Carefully clean away any dust or dirt that you discover, you might
find a mini vacuum cleaner usefull for this, so that all fans, filters,
grilles and heatsinks are as clean as possible. Please report back on what
temps the system now shows.
2) Observe and feel (with a moist hand) whether warm air can be felt
being pushed out of the back of the PC. Try to relate this to what you might
expect, given what air exits from other similar PCs you have. This should
occur when the PSU is warm enough for the fan to be running, and also from
any case exhaust fans you might have fitted. Report back. If air is exiting
the PC case, then it must be entering and so we know that there is some air
flowing inside the case. If anyone can suggest how the OP could measure the
airflow out of or in to the case, then that would be interesting.
I would also suggest that the OP temporarily re-sites the PC in question
in a relatively cool and open situation and observes the temperatures
reported by the system. Consider this to be an experiment to eliminate (or
otherwise) the possible adverse environmental effects of the PC's current
position (in a corner where the air has nowhere to go). If figures are
required for this experiment, then I would suggest the PC be placed on a
table approximately 0.8 to 1.0 metre high in a room at between 18 and 20
degrees celsius.
Kevin.
 
| Maintain all you want. Without learning basic theory, your
| experience could teach you nothing. You are being made the
| poster child of an 'experienced user' who forgot how to learn
| and therefore promotes myths. Myths that do not address the
| OPs original problem.
|
| You are working only from what you 'feel'; facts such as
| numbers be damned. You could not even post the incoming and
| outgoing temperatures - because to do so would have exposed
| the error in your 'feelings'. You are confronting fundamental
| science, tempered by decades of experience by using hearsay
| speculation. But again, your posts don't address the OP's
| original problem; a CPU temperature that may spike to 70
| degree C. One fan or seven still would not address his 70
| degree C problem - obviously. Please feel free to maintain
| the 'poster child' reasoning. It demonstrates why experience
| alone - no underlying theory - is only speculation. "I did
| this, that happened, but I don't know why" is what you have
| posted.

I'm not too sure exactly what you mean by 'poster child'. If it some sort
of attempt at a put-down then your arguments, in usenet parlance, are flames
and you are behaving in a troll-like manner. Please try to have some
respect for your fellow human beings and desist.
I'm not too sure what basic theory you believe I need to learn. fluid
mechanics, heat transfer and physical electronics were part of my degree
course - but I don't see that bandying qualifications around is likely to
help solve the OP's problem.
I'm not quite sure where 'seven fans' entered the argument. I am most
certainly not advocating that a PC case be fitted so.
The point is that the OP has started a thread discussing a problem of a
hot-running processor, and some of us are attempting to help solve this.
Unfortunately, we are not with the PC to observe it directly - so we have to
make suggestions, discuss ideas, and ask the OP to try things and report
back.
If the OP is able to measure the air temperature inside and outside the
case, and the airflow in and out, then those facts might well help to
diagnose the problem. If not, then we have only two choices. Either we
attempt to move forward without exact measurements, or we give up and go
home. Criticising the use of estimates and observations, when accurate
measurement is not possible, is far from helpfull. I have yet to notice you
actually contribute something usefull to this discussion. Insulting someone
who is trying to progress a problem, while suggesting nothing usefull
yourself, is far from helpfull.
Given that such issues as the mounting of the HSF and placement of ribbon
cables have been covered earlier in this thread, the OP has been asked to
make two observations - whether there has been a build-up of dust and dirt
inside the case of the PC and whether there is a flow of air through the PC
case. If you feel that it unreasonable to ask this without knowing that
exact inside and outside temperatures, then little progress can be made.
Maybe you feel that you have a very clever explanation for the cause of
the problem, but then why have you not presented it ?
You state that I have forgotten how to learn and promote myths. Learning
all the time, my friend, from both theory and practise. Quite what is it
exactly that you assert I am not learning ? How to avoid usenet trolls,
perhaps ?
You state that I am promoting 'myths'. Just what is it that I have said
that is a myth ?
I have promoted the concept of making sure that the HSF gets some change
of surrounding air, as if it is 'boxed in' by ribbon cables it could
re-cycle at least some of its used air and also the nearby ribbon cables
could adversely affect the airflow through it. If you feel that this is a
myth, then please say how you expect an HSF to work properly when wrapped in
a bundle of ribbon cables. If you feel that I have to conduct an experiment
to prove this by measurement, then by all means say so. I have encountered a
PC where a ribbon cable was lying flat across the face of the CPU fan -
close enough to occasionally touch and make a noise. The CPU would
occasionally run hot enough to trigger the BIOS alarm. I re-positioned the
ribbon cable and the problem went away - the CPU ran a bit cooler and the
alarm no longer sounded. At the time, I didn't consider exact measurement to
be absolutely necessary. I observed the CPU temp and the position of the
ribbon cable, and made a decision to move it based on experience. If you
feel that such things cannot possibly be true without making measurements,
then please say so. It would not exactly be difficult for me to conduct an
experiment to repeat this.
I have advocated using an intake filter to prevent a build-up of dust and
dirt within a PC, which I believe can impair cooling efficiency. I have also
stated that in order for the filter to work it is necessary to pull air
through it into the case, otherwise dirty air will enter through whatever
gaps and holes exist in the case. If you feel that this is a myth and that
either dust and dirt make no difference to cooling, a filter is not
necessary, or that air will naturally travel through the filter into the
case - instead of through other holes - without any sort of forced induction
then please say so. Quite what 'basic theory' you believe states that a
heatsink choked full of dust will work as well as a clean one I am not
familiar with. The 'basic theory' that I am using is that the surface of the
heatsink needs to be in contact with the air for heat to be conducted from
heatsink to air. If that is a myth then please state so. Perhaps we could
both conduct experiments and compare results ? I expect that it would be
usefull to record the CPU temperature after a steady-state had been reached.
Also, the total surface area of the heatsink and the flow of the fan could
be recorded.
One other point I have made is that obstructions in the path of the air to
or from a fan can lead to the generation of turbulance which creates noise.
If you consider this to be a myth, then I would suggest that we both conduct
experiments to prove the point one way or another. If you do not feel that a
subjective estimate of the amount of noise produced would suffice, then we
could use equipment to measure the sound pressure level.
Hopefully, the OP will let us know at some point the details which have
been asked about the problematic PC. If you have some enquiries or
suggestions to make to help persue a solution then I am sure they will be
welcomed.
Kevin.
 
Concepts are demonstrated by application notes from
heatsink manufacturers. First bottleneck for thermal
conductivity occurs at each medium transition. A transition
from 'CPU to heatsink' creates thermal resistance. That
thermal resistance increases if the transition is 'CPU to
thermal compound to heatsink'. Another major interface
involves the 'heatsink to air' interface.

Major thermal bottlenecks occur at these interfaces.
Pentium II and III "passively" cooled systems would reduce
thermal resistance by placing power supply fan so that air
flowed over CPU heatsink. Again, does not matter whether fan
blows or sucks. Important parameter is a number called LFM -
amount of air that passes across heatsink surface. As airflow
increases, its cooling effects decrease exponentially meaning
a large increase in airflow provides little increase in
heatsink cooling.

To minimize 'heatsink to air' interface, we now use HSF
(heatsink fans). Massive airflow makes a minor increase in
heat removal. Since a CPU fan provides maximum air flow
around and across a heatsink, then no external airflow will
contribute anything useful.

Manufacturer provides one number to summarize this entire
assembly - all three above paragraphs: degree C per watt. As
an example, HSF of 0.5 degree C per watt is proposed. Finally
some numbers.

Now for those chassis fans. Using a single 80 mm fan, the
typical system might see a 9 degree C difference between
incoming and outgoing temperature. Two fans might result in a
5 degree C difference. Seven fans might result in a 1.3
degree difference. Let's assume the CPU is located at hottest
spot inside that chassis. Let's assume no heat is removed by
metal chassis. IOW we worst case everything for a typically
sized system. Even with only one fan, CPU will experience 9
degrees C above room temperature air. A 75 watt CPU will be
25 degrees warmer than adjacent air. With one fan, CPU should
be 34 degrees warmer than room temperature. A 70 degree F
room should leave CPU at, worst case, 54 degree C using one
fan or 47 degree C using seen fans. IOW CPU is 36 degrees C
below maximum normal temperature with one chassis fan or 43
degrees C below maximum normal temperature with seven fans.
More fans provide virtually no improvement.

The OP complains of a 70 degree C CPU temperature spike.
Will more chassis fans solve this problem? Of course not as
numbers demonstrate. Even when using a rather average 0.5
degree C per watt heatsink, CPU should never be that hot.
Solution is not found with more fans. Increasing one fan to
seven provides no significant temperature reductions. The OP
typically should suspect a problem somewhere in the CPU HSF
assembly where bad thermal interfaces traditionally cause
major temperature increases and are easily created.

Was this 70 degree spike really a temperature increase?
Unanswered were some important questions such as where
temperature was being measured and by what? Also how long
were these temperature spikes? For some reason, CPU is
getting 15 degrees C hotter than even a worse case calculation
- assuming the heatsink fan assembly was average. Reasons for
an unexplained 15 degree C of heat must be identified. More
chassis fans will not create a 15 degree C reduction, which
leaves a problem within CPU HSF assembly or with how
temperature is being measured.
 
Kevin Lawton said:
You state that I have forgotten how to learn and promote myths. Learning
all the time, my friend, from both theory and practise. Quite what is it
exactly that you assert I am not learning ? How to avoid usenet trolls,
perhaps ?
Click to expand...

I think w_tom is either a 'bot or an idiot savant. Once you get past
his hand-waving and attempt to pin him down on specifics, he very
rapidly goes quiet. If you google for his posts, he posts almost
exclusively to threads such as this about cooling (and in particular
threads which refer to lightning protection and/or power surges, in
which he recommends solutions that are appropriate to his location,
North America, but useless for UK/Europe.)

His favourite phrases are "show us the numbers" and "junk science" but
he never has any useful data to contribute himself.

He has also been asked repeatedly not to top-post.

In short, yes, he is a troll.
 
I think w_tom is either a 'bot or an idiot savant. Once you get past
his hand-waving and attempt to pin him down on specifics, he very
rapidly goes quiet. If you google for his posts, he posts almost
exclusively to threads such as this about cooling (and in particular
threads which refer to lightning protection and/or power surges, in
which he recommends solutions that are appropriate to his location,
North America, but useless for UK/Europe.)
Click to expand...

He pops up in the most unlikely places as soon as there is a mention of
the above subjects. w_tom, if he exists, might be running a scanbot for
mention of overheating, surges, etc, and then jumps in with both feet,
dispenses his 'wisdom' and leaves, unwilling to be challenged in any
way.

The man's a twat, and I killfiled him a long time ago.
 
, perhaps ?
I think w_tom is either a 'bot or an idiot savant. Once you get past
his hand-waving and attempt to pin him down on specifics, he very
rapidly goes quiet. If you google for his posts, he posts almost
exclusively to threads such as this about cooling (and in particular
threads which refer to lightning protection and/or power surges, in
which he recommends solutions that are appropriate to his location,
North America, but useless for UK/Europe.)

His favourite phrases are "show us the numbers" and "junk science" but
he never has any useful data to contribute himself.

He has also been asked repeatedly not to top-post.

In short, yes, he is a troll.
Click to expand...

This has been my experience. I made the mistake of trying to hold a sensible
discussion with him about the use of thermal pastes versus heat pads, but it
quickly became obvious that he doesn't actually build PCs. He advised one
poster to try and run without either heat pad or paste because he feels the
heatsink manufacturers should provide mirror image lapped surfaces. He
doesn't think a 5c reduction in CPU temperature is material! Tell that to an
overclocker (like me). I did ask him to give us the benefit of his
experience by providing some real life figures based on his experience (as I
did with him), but surprise, surprise.....nothing.

I don't get caught up with him now.

Martin
 
| Concepts are demonstrated by application notes from
| heatsink manufacturers. First bottleneck for thermal
| conductivity occurs at each medium transition. A transition
| from 'CPU to heatsink' creates thermal resistance. That
| thermal resistance increases if the transition is 'CPU to
| thermal compound to heatsink'. Another major interface
| involves the 'heatsink to air' interface.
|
| Major thermal bottlenecks occur at these interfaces.
| Pentium II and III "passively" cooled systems would reduce
| thermal resistance by placing power supply fan so that air
| flowed over CPU heatsink. Again, does not matter whether fan
| blows or sucks. Important parameter is a number called LFM -
| amount of air that passes across heatsink surface. As airflow
| increases, its cooling effects decrease exponentially meaning
| a large increase in airflow provides little increase in
| heatsink cooling.
|
| To minimize 'heatsink to air' interface, we now use HSF
| (heatsink fans). Massive airflow makes a minor increase in
| heat removal. Since a CPU fan provides maximum air flow
| around and across a heatsink, then no external airflow will
| contribute anything useful.
|
| Manufacturer provides one number to summarize this entire
| assembly - all three above paragraphs: degree C per watt. As
| an example, HSF of 0.5 degree C per watt is proposed. Finally
| some numbers.
|
| Now for those chassis fans. Using a single 80 mm fan, the
| typical system might see a 9 degree C difference between
| incoming and outgoing temperature. Two fans might result in a
| 5 degree C difference. Seven fans might result in a 1.3
| degree difference. Let's assume the CPU is located at hottest
| spot inside that chassis. Let's assume no heat is removed by
| metal chassis. IOW we worst case everything for a typically
| sized system. Even with only one fan, CPU will experience 9
| degrees C above room temperature air. A 75 watt CPU will be
| 25 degrees warmer than adjacent air. With one fan, CPU should
| be 34 degrees warmer than room temperature. A 70 degree F
| room should leave CPU at, worst case, 54 degree C using one
| fan or 47 degree C using seen fans. IOW CPU is 36 degrees C
| below maximum normal temperature with one chassis fan or 43
| degrees C below maximum normal temperature with seven fans.
| More fans provide virtually no improvement.
|
| The OP complains of a 70 degree C CPU temperature spike.
| Will more chassis fans solve this problem? Of course not as
| numbers demonstrate. Even when using a rather average 0.5
| degree C per watt heatsink, CPU should never be that hot.
| Solution is not found with more fans. Increasing one fan to
| seven provides no significant temperature reductions. The OP
| typically should suspect a problem somewhere in the CPU HSF
| assembly where bad thermal interfaces traditionally cause
| major temperature increases and are easily created.
|
| Was this 70 degree spike really a temperature increase?
| Unanswered were some important questions such as where
| temperature was being measured and by what? Also how long
| were these temperature spikes? For some reason, CPU is
| getting 15 degrees C hotter than even a worse case calculation
| - assuming the heatsink fan assembly was average. Reasons for
| an unexplained 15 degree C of heat must be identified. More
| chassis fans will not create a 15 degree C reduction, which
| leaves a problem within CPU HSF assembly or with how
| temperature is being measured.

No-one is trying to argue against scientific fact, here. We all agree on
the mechanisms involved and recognise the problems of transferring heat
across a materials interface.
The aim is to try to address OP's problem as originally posted, and
bickering will not help that.
Contributing something which is actually helpfull and move things forward
will.
On that score - either put up or shut up.
Kevin.
 
Kevin Lawton wrote:

snip other useful suggestions
I would also suggest that the OP temporarily re-sites the PC in question
in a relatively cool and open situation and observes the temperatures
reported by the system. Consider this to be an experiment to eliminate (or
otherwise) the possible adverse environmental effects of the PC's current
position (in a corner where the air has nowhere to go). If figures are
required for this experiment, then I would suggest the PC be placed on a
table approximately 0.8 to 1.0 metre high in a room at between 18 and 20
degrees celsius.
Kevin.
Click to expand...

Definitely :)

Has it been established whether the reported CPU temperature is even
accurate?
Maybe it's time to borrow an IR thermometer and see if the sensor or
software is accurately reporting the temperatures.
I'm assuming we don't want to be drilling holes in the heatsink for
thermocouples :)

If there is an easy place to measure the *actual* core voltage with a
good DMM, this may not be a bad next move either...

Lee
 
Provided is exactly what the OP required: numbers that
demonstrate where a problem and solution must exist. Numbers
that demonstrate what was posted previously: chassis fans -
even seven chassis fans - don't solve his problem. One
chassis fan is more than sufficient.

If numbers and concepts are too complicated, then simply
reread the last paragraph - in a post that only attacks the
problem and misguided science (does not attack any person):
Was this 70 degree spike really a temperature increase?
Unanswered were some important questions such as where
temperature was being measured and by what? Also how long
were these temperature spikes? For some reason, CPU is
getting 15 degrees C hotter than even a worse case calculation
- assuming the heatsink fan assembly was average. Reasons for
an unexplained 15 degree C of heat must be identified. More
chassis fans will not create a 15 degree C reduction, which
leaves a problem within CPU HSF assembly or with how
temperature is being measured.
Click to expand...

Possible that a temperature spike does not really exist
which is why the above questions were posted. However I
suspect the OP has long since left since so much ill informed
speculations were posted as solutions; such as "More Air" or
"More Fans". Numbers (fundamental theory), real world
measurements using a thermometer, and even basic experience
tempered by knowledge all say this problem is not solved by
more fans and other such wild speculation. Posted is what was
repeatedly requested when I said, "provide numbers" to support
that 'more fan' speculation. Numbers say, and again, that
more fans and larger air holes are not a solution. Stick to
facts and numbers. Instead of attacking this poster (as other
junk scientists must do), please demonstrate a flaw in those
numbers (as a logical and unemotional scientist does).
Bluntly attack those numbers - not people.

Posted is an attack on outright misinformation - which, for
some silly reasons, you regard as a personal attack. The
numbers are what junk scientists never provide. Finally, in a
last post, you attempted to provide numbers. Good. But the
relationship between CFM and internal chassis temperature was
only speculation and was not correct. Your reasoning required
more advanced math - ie calculus or fractal type
calculations. Also in error was CFM for one fan. Number that
is obtained in fan manufacturer's datasheets. Posted, in
response were corrected numbers. Example: a typical 80 mm fan
should result in a 9 degree C temperature difference - worst
case.

Why do you attack the poster rather than learn how to
perform these calculations? Many 'computer experts' have
identified themselves for doing same thing previously -
posting junk science reasoning. Please don't be like those
other junk scientists - foolishly attacking the messenger.
Reasoning for how much a fan may cool was a honest, beginner's
attempt. But performed without having learned underlying
concepts. At least you finally tried to provide numbers.
Good. You could have also asked to learn what you (apparently)
did not know rather than, again, personally attack this
poster.

Reposted is a summary paragraph that focuses on the original
problem. Instead of attacking this poster, why not
concentrate on that paragraph? What do I keep going back to?
Addressing the OPs original problem by demanding numbers.
Calculations suggest a ballpark 15 degree C problem that
should not exist. A problem that obviously cannot be solve
with "more fans".
 
| Provided is exactly what the OP required: numbers that
| demonstrate where a problem and solution must exist. Numbers
| that demonstrate what was posted previously: chassis fans -
| even seven chassis fans - don't solve his problem. One
| chassis fan is more than sufficient.
|
| If numbers and concepts are too complicated, then simply
| reread the last paragraph - in a post that only attacks the
| problem and misguided science (does not attack any person):
|| Was this 70 degree spike really a temperature increase?
|| Unanswered were some important questions such as where
|| temperature was being measured and by what? Also how long
|| were these temperature spikes? For some reason, CPU is
|| getting 15 degrees C hotter than even a worse case calculation
|| - assuming the heatsink fan assembly was average. Reasons for
|| an unexplained 15 degree C of heat must be identified. More
|| chassis fans will not create a 15 degree C reduction, which
|| leaves a problem within CPU HSF assembly or with how
|| temperature is being measured.
|
| Possible that a temperature spike does not really exist
| which is why the above questions were posted. However I
| suspect the OP has long since left since so much ill informed
| speculations were posted as solutions; such as "More Air" or
| "More Fans". Numbers (fundamental theory), real world
| measurements using a thermometer, and even basic experience
| tempered by knowledge all say this problem is not solved by
| more fans and other such wild speculation. Posted is what was
| repeatedly requested when I said, "provide numbers" to support
| that 'more fan' speculation. Numbers say, and again, that
| more fans and larger air holes are not a solution. Stick to
| facts and numbers. Instead of attacking this poster (as other
| junk scientists must do), please demonstrate a flaw in those
| numbers (as a logical and unemotional scientist does).
| Bluntly attack those numbers - not people.
|
| Posted is an attack on outright misinformation - which, for
| some silly reasons, you regard as a personal attack. The
| numbers are what junk scientists never provide. Finally, in a
| last post, you attempted to provide numbers. Good. But the
| relationship between CFM and internal chassis temperature was
| only speculation and was not correct. Your reasoning required
| more advanced math - ie calculus or fractal type
| calculations. Also in error was CFM for one fan. Number that
| is obtained in fan manufacturer's datasheets. Posted, in
| response were corrected numbers. Example: a typical 80 mm fan
| should result in a 9 degree C temperature difference - worst
| case.
|
| Why do you attack the poster rather than learn how to
| perform these calculations? Many 'computer experts' have
| identified themselves for doing same thing previously -
| posting junk science reasoning. Please don't be like those
| other junk scientists - foolishly attacking the messenger.
| Reasoning for how much a fan may cool was a honest, beginner's
| attempt. But performed without having learned underlying
| concepts. At least you finally tried to provide numbers.
| Good. You could have also asked to learn what you (apparently)
| did not know rather than, again, personally attack this
| poster.
|
| Reposted is a summary paragraph that focuses on the original
| problem. Instead of attacking this poster, why not
| concentrate on that paragraph? What do I keep going back to?
| Addressing the OPs original problem by demanding numbers.
| Calculations suggest a ballpark 15 degree C problem that
| should not exist. A problem that obviously cannot be solve
| with "more fans".

Okay. I am not disagreeing with your concept that empirical facts -
numbers - will help us to determine the cause of the OP's problem.
Unfortunately, the only numerical data so far supplied from the OP relates
to the CPU and m,/board reported temperatures. I realise that these might
not be wholly accurate due to the mechanism involved in measuring them.
Attempting to understand the problem from the point of view of materials
science and fluid mechanics is fine so long as you can suggest ways the OP
can provide the measurements you require. We have yet to see you explain to
the OP how to perform these measurements.
We seem to agree that, provided there is some sort of airflow through the
PC case, a correctly assembled HSF and CPU should run within a reasonable
temperature ange under normal conditions. I believe that this leaves us with
four alternatives:
1) That the deployment or assembley of the HSF onto the CPU is somehow at
fault. Either the HSF is not working correctly, maybe due to the fan not
spinning or a severe dust build-up, or heat is not being transferred from
CPU to heat-sink.
2) That the fan on the heat-sink is repeatedly cycling the same air
through it which is heating up, ie: there is no significant airflow through
the PC case. No matter how good the HSF is, it cannot cool the CPU below the
temperature of the air passing through it.
3) That at the time of the reported seventy degree CPU temperature, the
CPU was subject to an abnormal load and became hotter as a result. Examples
of what might cause this include, but are not limited to, overclocking
and/or increased core voltage.
4) That the measurement of the reported CPU temperature is at fault and
the CPU is not actually running at seventy degrees.
If yopu actually disagree with the above then please state so and why.
For some reason you keep using 'seven fans' as an attempt to dispute
anything I have suggested, though at no time have I advocated using a large
number of chassis fans in this case.
Actually, I have stated two points on this subject:
1) That the HSF will not be able to effectively maintain a reasonable CPU
temperature over a long period of continuous operation unless there is some
airflow. It will not work properly in a sealed box and some change of air is
required. To this end I have suggested that one fan should be more than
sufficient in most circumstances. From the perspective of getting some air
to flow, the fan in the PSU could be sufficient if it were to operate
continuously.
2) It is strongly desirable to ensure that the air entering the CPU case
is filtered in order to avoid a build-up of dust and dirt which will impair
colling efficiency and contribute towards overheating. Obviously in order
for this to work the air has to be encouraged to flow through the filter and
not enter the PC case through other openings. I did not suggest that a
seventy degree temperature spike was likely to be caused by dust alone.
If you do actually disagree with either of the above statements, then
please say why you feel they are not accurate.
The figures I gave were purely hypothetical and used to illustrate a
point.
I also stated that using an intake fan would ensure that the air entering
the case would pass through the filter.
My points are based on experience gained from working on PCs and other
computer systems over a long period of time. I am in no way attempting to
dispute or ignore the underlying science but I acknowledge the difficulties
the OP might encounter in providing accurate measurements of temperature and
airflow. Straightforward observation can be a usefull diagnostic toll under
such circumstances, and I have therefore asked the OP to make certain
observations and report back. If, for example, the OP obseves that the HSF
is choked full of dust and dirt it does not require a precise measurement in
order know that cleaning that dust and dirt from the HSF would be a good
thing to do.
Kevin.
 
| |
||| Cutting out grills for better cooling is a waste of time,
||
|| Oh no it isn't !
|| Quite often case grills are just a few concentric circles of
|| small holes. Their total area might amount to less than two
|| square inches. An three-inch fan has an area of around six
|| square inches, and axial fans an't deliver much pressure.
|| The net result is that the little holes will both reduce
|| airflow by increasing air resistance and crate turbulence.
|
|| 1) Try running a case fan in free air without a grille.
|| Notice how quite it is.
|
| You are absolutely correct that it's quite -- quite quite, in fact.

Okay, my brain was going faster than my fingers could type and I made a
slight spelling mistake.
I was showing that a case fan run in free air without a grille is quiet,
quite quiet in fact.

|| 2) Try blowing with your mouth into free air, and then
|| at or through an empty PC case fan grille. Notice how much
|| noise the air makes as it impinges on grille. Notice also
|| how not all of the air you are blowing passes through
|| the grille, but bounces off the metal instead.
|
| It's good that you're not one of those people who obsesses about
| cooling for the sake of cooling and who performs proper systematic
| testing and doesn't use ad hoc methods that are subject to great bias.

In this case I was illustrating a point that the PC case fan grilles
increase noise by causing turbulance as they disturb the passage of air from
the fan. Precise empirical measurement was not absolutely necessary in order
to demonstrate the principle, which is that when a fan has to push (or pul)
air through the little holes of a typical PC case fan grille it can generate
noticable noise.

Are you disagreeing with me, or just taking the piss ?
 
Two things here...

It is not strongly desired to filter air into PC cases
o Air filters introduce a static resistance of 15-45Pa (clean-dirty)
o DC Tubeaxial fans as fitted to PCs are not suited to filter use
--- glancing at P-Q curves will show how airflow falls with resistance
--- resistance of even 15Pa will significantly reduce airflow
--- resistance of just 30Pa will essentially collapse airflow
o Fan depth &/or size must be greatly increased
--- compensate by more cfm for a given static-pressure
--- unfortunately noise will increase correspondingly

PCs do not require a lot of cooling
o CPU+Graphics+RAM/HD = 105+55+45 = 200W max at 100%
o PSU at 80% efficiency draws 240W, dissipates 40W itself
o 300cfm cools 1500W, 50cfm will cool 250W
o If a PSU fan is 25cfm, case fan 25cfm, done

More cooling can be required due to resistance
o If you fit filters, then greater-fan depth or cfm is required to compensate
--- you need 50cfm, you fit filters of 30Pa resistance (60% clogged)
--- from the P-Q curves you read the cfm at 30Pa resistance
--- then scale fan size / depth / qty to get back to 50cfm (at 30Pa)
o If your intake or exhaust grills are punched metal, consider a change
--- punched case slots/holes are often just 45-55% free air
--- round-wire-grills are 89-91% free air = more cfm & less noise
o Your cfm is determined by the weakest link - the intake
--- not usually the fan punching
--- more usually the slot in the plastic front fascia - 3"x1"
--- 3"x1" slot = 1900mm^2 vs 2x80mm exhaust = 9000mm^2

All are really quite minor changes, and good cases don't need them.

CPU cooler:
o CPU coolers are measured in degrees-Centrigrade-per-Watt (oC/W)
o The oC/W must be low enough to keep the CPU in reasonable limits

If the case is removing air sufficiently - the CPU will only be recirculating
its own air at the known design spec (re quoted oC/W). If the case is not
removing air sufficiently, the CPU cooler will recirculate more of the air it
has just heated and so the realised oC/W will fall re lower delta-T.

It is worth noting that some CPU coolers are over-rated re spec, this is
more common for AMD processors than Intel - altho that will change as
the P4-Prescott comes in (P4-3.2N cooler 45-46oC, P4-3.2P using the
same cooler was 64-65oC; some report m/b components >>100oC too).

The problem can occur with over-use of heatsink compound
o Two flat surfaces only make perfect contact at 3 points
o Heatsink compound is just to fill in that ultra-thin gap
o Spreading it like margarine does not help heat transfer

The problem can also occur with incorrectly or marginally seated heatsinks.

A very considerable problem is temperature reporting accuracy:
o Most thermistors are +/- 10% in accuracy & calibration
---- actual 50oC -- one board may read 45oC, another 55oC - 10oC gap
o It is not inconceivable for thermistor to be vastly out of spec
---- both in calibration & accuracy, to a combined figure of 20%
---- actual 50oC -- in-spec board reads 45oC, out-of-spec 60oC - 15oC gap

Rarely - but consistently - some very odd temperature readings are reported,
either overly low or overly high relative to the normal distribution of reports.

So several avenues of attack, but ones based on cause:effect, cost:benefit.
Most quite high-spec PCs require 50cfm of exhaust airflow, unless someone
has fitted fan filters or has the exhaust fans sucking thro a tiny intake slot. It
is better to fix the intake slot than stick a NASA windtunnel on the exhaust.

Roll on BTX, at least there will be a proper OPEN intake grill in the case front.
Apple got it right, then stuck too many fans in the thing. G4 Tower got the size
of heatsink right, the fan size right, but then stuck a 150cfm 57dB(A) fan in.
 
Dorothy said:
Roll on BTX, at least there will be a proper OPEN intake grill in the case front.
Apple got it right, then stuck too many fans in the thing. G4 Tower got the size
of heatsink right, the fan size right, but then stuck a 150cfm 57dB(A) fan in.
Click to expand...

Interesting post, thank you.

It is possible to have too many fans. One optional case fan I added in
started making a lot of noise, so I removed it, and the effect on PC
temp was virtually nil.
 
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