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Maximum room temperature



 
 
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  #1  
Old February 18th 09, 06:41 AM posted to alt.comp.hardware.overclocking
baggins2000
external usenet poster
 
Posts: 2
Default Maximum room temperature

What would be the recommended maximum room temperature for operating
an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to
overclock, but I guessed that people here would know more about the
thermal aspects of CPU operation.

  #2  
Old February 18th 09, 08:17 AM posted to alt.comp.hardware.overclocking
Paul
external usenet poster
 
Posts: 13,364
Default Maximum room temperature

baggins2000 wrote:
What would be the recommended maximum room temperature for operating
an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to
overclock, but I guessed that people here would know more about the
thermal aspects of CPU operation.


According to this, the max temp for the 125W 9950 is 61C.
I'd like to dig up more info for you (like verifying in a
processor spec document, that what is printed here is
accurate), but the AMD web site doesn't make that easy.
I'm not even sure there is a separate thermal spec as such.

http://products.amd.com/en-us/Deskto...il.aspx?id=447

Two aspects of cooling are important in a computer.
There is the ability of the rear exhaust fan, to pull hot
air out of the computer case. That is important, because
otherwise heat would build up inside the case. If you
sealed the computer case, the stuff inside would be boiled
alive.

The CPU fan moves heat from the CPU heatsink, into the
internal computer case air. The CPU cooler cannot do its
job, without a well cooled case.

If your motherboard has a "case temperature" sensor, then
you can get some idea of how well it is cooled.

For example, let's do some arithmetic.

Say the room temperature is currently 25C.

One article I read, declared that a well cooled computer case
(one with adequate rear exhaust fan), would allow the internal
case temperature to reach 7C higher, or 32C. That requires
a relatively good airflow (fan won't be silent).

Using those assumptions, we can work out the requirements of
the CPU heatsink. If 61C is the CPU max case temp, and 32C is the
internal air temp, the difference is 61C - 32C. We assume the
CPU is running at 100%, with all cores running at max. Say,
a copy of the latest Prime95 executable with multithreading
is running. The above product listing says the TDP of the processor
is 125W. That is purely an estimate, and the real power can
be exactly equal to that, or a value which is quite different.
(For example, my current 65W TDP CPU, never draws more than
36W, meaning it runs a lot cooler than the spec says. Still,
we have to make some assumption, to do the arithmetic.)

The ratio of delta_T to power in watts, is called Theta_R or
the thermal resistance. We can work out the heatsink required
now.
61C - 32C
Theta_R = ---------- = 0.23 C/W
125W

Now, we compare that to a Zalman CNPS9700. If the fan runs at
full speed on that particular CPU cooler, Theta_R is 0.12 C/W.
That means, in the above arithmetic, we meet the requirements.
I found that number on this site - the number is no longer
listed on the Zalman site. And many companies don't want to
give this number, because it makes cooling design too easy.

http://www.crazypc.com/products/50992.html

We can also work out, what the maximum internal case temperature
can be, using our new CNPS9700 heatsink.

61C - X
0.12C/W = ---------- , 61C - (0.12C/W * 125W) = X = 46C
125W

Since we've defined the case to be 7C hotter than the room,
and X is 46C, we know the room is 39C. Therefore, if we use
the fancy Zalman 9700 family cooler (like the 9700NT with four
pin fan connector), we can allow the room temperature to hit 39C,
and at that point the CPU will be at 61C. But, remembering as well,
that there must be sufficient airflow through the case, such that
the internal case air is only 7C warmer than the room.

By now, you might be saying, "how can I figure out what fan to
use for the case ?". Well, there is an equation for that too.
Now, for this one, you need to know all the thermal loads inside
the computer case. We have the 125W processor, say a 100W
video card, two 12W hard drives, say a total of 250W. Our definition
of a well cooled case, is 7C, which is equal to 12.6 Fahrenheit degrees.
Plugging in the values.

CFM = 3.16 * Watts / Delta_T_degrees_F

CFM = 3.16 * 250W / 12.6F = 62.7 cubic feet per minute.

Now we go shopping.

The Newegg fan page, Advanced search option, has the ability
to select a range of CFM. I picked this cheap fan from the
search result.

http://www.newegg.com/Product/Produc...82E16811998124

Fan Size 120mm
RPM 1700rpm
Air Flow 63.85CMF
Noise Level 29.67dBA

This fan meets our cubic feet per minute requirement. It allows
the room to reach 39C while the processor runs flat out. However,
the noise level is about 30dBA, which is a rough number for
"man, this fan is annoying". Now, if we use a fan controller
knob, to slow the fan down, and say run it at 70% of full speed,
the computer case air gets warmer. Say it gets warmer by 3C,
then we'd have to drop out maximum room temperature by 3C as
a result. So you can trade noise, for max room temperature.
With a slightly quieter fan (or a noisy fan with voltage
reduction), we might take a room temp of 36C.

Now, when my room hits that temp, I'm usually not interested in
sitting in front of the computer, and I head out on the patio.
You'd have to be paying me, to sweat in that.

Another question would be, how hot is the hard drive. I cannot
answer that one. I personally treat hard drives better than I
treat CPUs, and would be monitoring the hard drive more closely
than the CPU. The CPU has its own protection mechanisms - if the
heatsink on the CPU falls off, the CPU will actually shut off
the ATX power supply without warning (so there is no opportunity
to save your work - the power just goes off). So the CPU will
protect itself, if something nasty happens. The same cannot
be said for the hard drive, which cannot defend itself.

Note that the above "29.67dBA" noise figure is pure fantasy.
No two people measure noise the same way, so you cannot
compare the numbers you find in catalog listings. Instead,
read the customer reviews and "average" out what they
say about noise. That is a better indicator than the
29.67 number. Still, as mentioned previously, if you
cannot get customer reviews, sometimes you're forced to
rely on that 29.67dBA number.

Having written all that, perhaps now you can explain to me,
what you plan to do. Are you going to put the computer
in a crawl space or a closet ? Well, don't do that.
Computers need to breathe, to stay cool.

HTH,
Paul
  #3  
Old February 18th 09, 06:12 PM posted to alt.comp.hardware.overclocking
Oldfart
external usenet poster
 
Posts: 4
Default Maximum room temperature



Paul wrote:
baggins2000 wrote:
What would be the recommended maximum room temperature for operating
an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to
overclock, but I guessed that people here would know more about the
thermal aspects of CPU operation.


According to this, the max temp for the 125W 9950 is 61C.
I'd like to dig up more info for you (like verifying in a
processor spec document, that what is printed here is
accurate), but the AMD web site doesn't make that easy.
I'm not even sure there is a separate thermal spec as such.

http://products.amd.com/en-us/Deskto...il.aspx?id=447

Two aspects of cooling are important in a computer.
There is the ability of the rear exhaust fan, to pull hot
air out of the computer case. That is important, because
otherwise heat would build up inside the case. If you
sealed the computer case, the stuff inside would be boiled
alive.

The CPU fan moves heat from the CPU heatsink, into the
internal computer case air. The CPU cooler cannot do its
job, without a well cooled case.

If your motherboard has a "case temperature" sensor, then
you can get some idea of how well it is cooled.

For example, let's do some arithmetic.

Say the room temperature is currently 25C.

One article I read, declared that a well cooled computer case
(one with adequate rear exhaust fan), would allow the internal
case temperature to reach 7C higher, or 32C. That requires
a relatively good airflow (fan won't be silent).

Using those assumptions, we can work out the requirements of
the CPU heatsink. If 61C is the CPU max case temp, and 32C is the
internal air temp, the difference is 61C - 32C. We assume the
CPU is running at 100%, with all cores running at max. Say,
a copy of the latest Prime95 executable with multithreading
is running. The above product listing says the TDP of the processor
is 125W. That is purely an estimate, and the real power can
be exactly equal to that, or a value which is quite different.
(For example, my current 65W TDP CPU, never draws more than
36W, meaning it runs a lot cooler than the spec says. Still,
we have to make some assumption, to do the arithmetic.)

The ratio of delta_T to power in watts, is called Theta_R or
the thermal resistance. We can work out the heatsink required
now.
61C - 32C
Theta_R = ---------- = 0.23 C/W
125W

Now, we compare that to a Zalman CNPS9700. If the fan runs at
full speed on that particular CPU cooler, Theta_R is 0.12 C/W.
That means, in the above arithmetic, we meet the requirements.
I found that number on this site - the number is no longer
listed on the Zalman site. And many companies don't want to
give this number, because it makes cooling design too easy.

http://www.crazypc.com/products/50992.html

We can also work out, what the maximum internal case temperature
can be, using our new CNPS9700 heatsink.

61C - X
0.12C/W = ---------- , 61C - (0.12C/W * 125W) = X = 46C
125W

Since we've defined the case to be 7C hotter than the room,
and X is 46C, we know the room is 39C. Therefore, if we use
the fancy Zalman 9700 family cooler (like the 9700NT with four
pin fan connector), we can allow the room temperature to hit 39C,
and at that point the CPU will be at 61C. But, remembering as well,
that there must be sufficient airflow through the case, such that
the internal case air is only 7C warmer than the room.

By now, you might be saying, "how can I figure out what fan to
use for the case ?". Well, there is an equation for that too.
Now, for this one, you need to know all the thermal loads inside
the computer case. We have the 125W processor, say a 100W
video card, two 12W hard drives, say a total of 250W. Our definition
of a well cooled case, is 7C, which is equal to 12.6 Fahrenheit degrees.
Plugging in the values.

CFM = 3.16 * Watts / Delta_T_degrees_F

CFM = 3.16 * 250W / 12.6F = 62.7 cubic feet per minute.

Now we go shopping.

The Newegg fan page, Advanced search option, has the ability
to select a range of CFM. I picked this cheap fan from the
search result.

http://www.newegg.com/Product/Produc...82E16811998124

Fan Size 120mm
RPM 1700rpm
Air Flow 63.85CMF
Noise Level 29.67dBA

This fan meets our cubic feet per minute requirement. It allows
the room to reach 39C while the processor runs flat out. However,
the noise level is about 30dBA, which is a rough number for
"man, this fan is annoying". Now, if we use a fan controller
knob, to slow the fan down, and say run it at 70% of full speed,
the computer case air gets warmer. Say it gets warmer by 3C,
then we'd have to drop out maximum room temperature by 3C as
a result. So you can trade noise, for max room temperature.
With a slightly quieter fan (or a noisy fan with voltage
reduction), we might take a room temp of 36C.

Now, when my room hits that temp, I'm usually not interested in
sitting in front of the computer, and I head out on the patio.
You'd have to be paying me, to sweat in that.

Another question would be, how hot is the hard drive. I cannot
answer that one. I personally treat hard drives better than I
treat CPUs, and would be monitoring the hard drive more closely
than the CPU. The CPU has its own protection mechanisms - if the
heatsink on the CPU falls off, the CPU will actually shut off
the ATX power supply without warning (so there is no opportunity
to save your work - the power just goes off). So the CPU will
protect itself, if something nasty happens. The same cannot
be said for the hard drive, which cannot defend itself.

Note that the above "29.67dBA" noise figure is pure fantasy.
No two people measure noise the same way, so you cannot
compare the numbers you find in catalog listings. Instead,
read the customer reviews and "average" out what they
say about noise. That is a better indicator than the
29.67 number. Still, as mentioned previously, if you
cannot get customer reviews, sometimes you're forced to
rely on that 29.67dBA number.

Having written all that, perhaps now you can explain to me,
what you plan to do. Are you going to put the computer
in a crawl space or a closet ? Well, don't do that.
Computers need to breathe, to stay cool.

HTH,
Paul


Excellent response, Paul. The only thing I would add is that in order to
flow the required air volume through the case there must be sufficient
intake area to accommodate the exhaust fan.

  #4  
Old February 18th 09, 08:50 PM posted to alt.comp.hardware.overclocking
Paul
external usenet poster
 
Posts: 13,364
Default Maximum room temperature

Oldfart wrote:

Excellent response, Paul. The only thing I would add is that in order to
flow the required air volume through the case there must be sufficient
intake area to accommodate the exhaust fan.


That's a good point, and something I had to fix on one of my computer cases.

One area I didn't address, is what happens when you use multiple fans.
The CFMs don't add together directly. Sometimes, one fan actually ends
up working against another fan (I had air blow *backwards* through
a hard drive cooler once - pretty funny). So I lack the technical details,
of how to deal with the air volume versus resistance curves and the
like. The CFM printed on the fan is not the whole story. But at least
it gets you into the right ballpark.

Paul

  #5  
Old February 20th 09, 01:04 AM posted to alt.comp.hardware.overclocking
Phil Weldon[_4_]
external usenet poster
 
Posts: 10
Default Maximum room temperature

'baggins2000' wrote:
What would be the recommended maximum room temperature for operating
an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to
overclock, but I guessed that people here would know more about the
thermal aspects of CPU operation.

_____

The short answer - it depends.

The maximum room temperature allowable depends on how good your heat sinks
and case ventilation are.

Very good heat sinks, along with good case ventilation will keep your
computer running at a room temperature too high to be healthy for you (say,
50 C or 122 F). On the other hand your particular CPU heatsink/fan
combination, other heat sinks, and the volume of air moved through the
system case might NOT be good enough. A better heatsink (larger, more fins,
more conductive metal, flatter/smoother/more parallel CPU interface, higher
air flow, and perhaps internal heat pipes) will have a lower thermal
resistance. That improvement gives a greater temperature difference between
the air entering the heatsink and the CPU/GPU/chipset/memory. CPUs (Intel
in particular) are designed to run properly under very hot conditions
because stuff happens - dirt and dust clogging the heatsink fins, poor case
ventilation, high room temperatures. Because the manufacturer doesn't want
returns. Since the Pentium 90 Intel CPUs have been protected from damage
caused by overheating. That is probably now true for recent AMD CPUs.

The ability to overclock depends on the individual processor, motherboard,
heat sinks, ventilation and power supplies stability. The maximum room
temperature for proper overclocked or non-overclocked operation depends on
the same things.

Phil Weldon

"baggins2000" wrote in message
...
What would be the recommended maximum room temperature for operating
an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to
overclock, but I guessed that people here would know more about the
thermal aspects of CPU operation.


  #6  
Old February 24th 09, 04:35 AM posted to alt.comp.hardware.overclocking
baggins2000
external usenet poster
 
Posts: 2
Default Maximum room temperature

Thanks, for the info

I'd would have to rate this as the best set of responses in 8yrs.
Very informative.

Maybe needs another post, but you mentioned Zalman fans. I have one,
but I am not that confident that I put in on correctly.

Do you have a recommendation on procedures for installing Zalman fans
or just about any of these larger fans. I'm always worried I'm going
to install this thing a little off of the chip. The first time I
tried to install it looked like I had left a 1/4 of an inch off of the
chip and the whole chip wasn't covered. And on one fan I'm having a
heck of a time checking the position (Zalman CNPS 7700 ALCU).

On Feb 19, 6:04*pm, "Phil Weldon" wrote:
'baggins2000' wrote:
What would be the recommended maximum room temperature for operating
an AMD Phenom 9950 with a mid-size Zantec fan. *I do not intend to
overclock, but I guessed that people here would know more about the
thermal aspects of CPU operation.


_____

The short answer - it depends.

The maximum room temperature allowable depends on how good your heat sinks
and case ventilation are.

Very good heat sinks, along with good case ventilation will keep your
computer running at a room temperature too high to be healthy for you (say,
50 C or 122 F). * On the other hand your particular CPU heatsink/fan
combination, other heat sinks, and the volume of air moved through the
system case might NOT be good enough. *A better heatsink (larger, more fins,
more conductive metal, flatter/smoother/more parallel CPU interface, higher
air flow, and perhaps internal heat pipes) will have a lower thermal
resistance. *That improvement gives a greater temperature difference between
the air entering the heatsink and the CPU/GPU/chipset/memory. *CPUs (Intel
in particular) are designed to run properly under very hot conditions
because stuff happens - dirt and dust clogging the heatsink fins, poor case
ventilation, high room temperatures. *Because the manufacturer doesn't want
returns. *Since the Pentium 90 Intel CPUs have been protected from damage
caused by overheating. *That is probably now true for recent AMD CPUs.

The ability to overclock depends on the individual processor, motherboard,
heat sinks, ventilation and power supplies stability. *The maximum room
temperature for proper overclocked or non-overclocked operation depends on
the same things.

Phil Weldon

"baggins2000" wrote in message

...

What would be the recommended maximum room temperature for operating
an AMD Phenom 9950 with a mid-size Zantec fan. *I do not intend to
overclock, but I guessed that people here would know more about the
thermal aspects of CPU operation.


  #7  
Old March 9th 09, 08:26 AM posted to alt.comp.hardware.overclocking
Phil Weldon[_4_]
external usenet poster
 
Posts: 10
Default Maximum room temperature

'Phil Weldon' wrote, in part:
'baggins2000' wrote:
What would be the recommended maximum room temperature for operating
an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to
overclock, but I guessed that people here would know more about the
thermal aspects of CPU operation.

_____

The short answer - it depends.

The maximum room temperature allowable depends on how good your heat sinks
and case ventilation are.

_____

CORRECTION; the fourth sentence in the third paragraph of my reply should
read:

That improvement gives a 'SMALLER' temperature difference between the air
entering the heatsink and the CPU/GPU/chipset/memory. (emphasis added)

My original reply incorrectly stated:

That improvement gives a greater temperature difference between the air
entering the heatsink and the CPU/GPU/chipset/memory.

Phil Weldon

"Phil Weldon" wrote in message
m...
'baggins2000' wrote:
What would be the recommended maximum room temperature for operating
an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to
overclock, but I guessed that people here would know more about the
thermal aspects of CPU operation.

_____

The short answer - it depends.

The maximum room temperature allowable depends on how good your heat sinks
and case ventilation are.

Very good heat sinks, along with good case ventilation will keep your
computer running at a room temperature too high to be healthy for you
(say, 50 C or 122 F). On the other hand your particular CPU heatsink/fan
combination, other heat sinks, and the volume of air moved through the
system case might NOT be good enough. A better heatsink (larger, more
fins, more conductive metal, flatter/smoother/more parallel CPU interface,
higher air flow, and perhaps internal heat pipes) will have a lower
thermal resistance. That improvement gives a greater temperature
difference between the air entering the heatsink and the
CPU/GPU/chipset/memory. CPUs (Intel in particular) are designed to run
properly under very hot conditions because stuff happens - dirt and dust
clogging the heatsink fins, poor case ventilation, high room temperatures.
Because the manufacturer doesn't want returns. Since the Pentium 90 Intel
CPUs have been protected from damage caused by overheating. That is
probably now true for recent AMD CPUs.

The ability to overclock depends on the individual processor, motherboard,
heat sinks, ventilation and power supplies stability. The maximum room
temperature for proper overclocked or non-overclocked operation depends on
the same things.

Phil Weldon

"baggins2000" wrote in message
...
What would be the recommended maximum room temperature for operating
an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to
overclock, but I guessed that people here would know more about the
thermal aspects of CPU operation.



  #8  
Old March 9th 09, 08:27 AM posted to alt.comp.hardware.overclocking
Phil Weldon[_4_]
external usenet poster
 
Posts: 10
Default Maximum room temperature

'Phil Weldon' wrote, in part:
'baggins2000' wrote:
What would be the recommended maximum room temperature for operating
an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to
overclock, but I guessed that people here would know more about the
thermal aspects of CPU operation.

_____

The short answer - it depends.

The maximum room temperature allowable depends on how good your heat sinks
and case ventilation are.

_____

CORRECTION; the fourth sentence in the third paragraph of my reply should
read:

That improvement gives a 'SMALLER' temperature difference between the air
entering the heatsink and the CPU/GPU/chipset/memory. (emphasis added)

My original reply incorrectly stated:

That improvement gives a greater temperature difference between the air
entering the heatsink and the CPU/GPU/chipset/memory.

Phil Weldon

"baggins2000" wrote in message
...
Thanks, for the info

I'd would have to rate this as the best set of responses in 8yrs.
Very informative.

Maybe needs another post, but you mentioned Zalman fans. I have one,
but I am not that confident that I put in on correctly.

Do you have a recommendation on procedures for installing Zalman fans
or just about any of these larger fans. I'm always worried I'm going
to install this thing a little off of the chip. The first time I
tried to install it looked like I had left a 1/4 of an inch off of the
chip and the whole chip wasn't covered. And on one fan I'm having a
heck of a time checking the position (Zalman CNPS 7700 ALCU).

On Feb 19, 6:04 pm, "Phil Weldon" wrote:
'baggins2000' wrote:
What would be the recommended maximum room temperature for operating
an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to
overclock, but I guessed that people here would know more about the
thermal aspects of CPU operation.


_____

The short answer - it depends.

The maximum room temperature allowable depends on how good your heat sinks
and case ventilation are.

Very good heat sinks, along with good case ventilation will keep your
computer running at a room temperature too high to be healthy for you
(say,
50 C or 122 F). On the other hand your particular CPU heatsink/fan
combination, other heat sinks, and the volume of air moved through the
system case might NOT be good enough. A better heatsink (larger, more
fins,
more conductive metal, flatter/smoother/more parallel CPU interface,
higher
air flow, and perhaps internal heat pipes) will have a lower thermal
resistance. That improvement gives a greater temperature difference
between
the air entering the heatsink and the CPU/GPU/chipset/memory. CPUs (Intel
in particular) are designed to run properly under very hot conditions
because stuff happens - dirt and dust clogging the heatsink fins, poor
case
ventilation, high room temperatures. Because the manufacturer doesn't want
returns. Since the Pentium 90 Intel CPUs have been protected from damage
caused by overheating. That is probably now true for recent AMD CPUs.

The ability to overclock depends on the individual processor, motherboard,
heat sinks, ventilation and power supplies stability. The maximum room
temperature for proper overclocked or non-overclocked operation depends on
the same things.

Phil Weldon

"baggins2000" wrote in message

...

What would be the recommended maximum room temperature for operating
an AMD Phenom 9950 with a mid-size Zantec fan. I do not intend to
overclock, but I guessed that people here would know more about the
thermal aspects of CPU operation.


 




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