Lowering PC temp

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Hi, even though this question is a little bit off topic I think you guys may
be able to help me:

I have a P4 that lives inside of a desk cabinet. The cabinet has a venting
fan, also the back of the cabinet has a 1'x1' cut-out into the sheet rock
wall behind it. When I use BurnMax to throttle up my CPU for several hours
the CPU is nearing its max suggested temp of 70'. I get a reading of about
62' inside of the cabinet. If I run it outside of the cabinet it is only 5'

I have a Zalman CNPS7700 CPU Cooler
(http://www.zalman.co.kr/eng/product/view.asp?idx=145&code=009 ) installed.
Another fan  vents out of the back of the case into the sheet rock chamber
behind the cabinet, and a third fan  vents through one of the PCI slots into
the sheet rock.

I think most of my heat buildup is coming from the power supply as it is
quite hot to the touch. I was considering mounting the power supply
externally in the sheet rock chamber. Any thoughts about this? Can the power
supply cables (Drive cables, cables going to MB, etc) be extended by 24".
Will the extended length be prone to any interference? Does anyone make a
power supply with really long cables, or extension cables that can be added
to the current PS?

Are there 'cool' running PS?

Any other ideas or thoughts regarding lowering my temp by 10' or so.


Re: Lowering PC temp

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I'm confused by your post..  If the CPU is running only
5 degrees cooler outside the cabinet, how will moving the
PS (i.e. even less airflow) help?  At least from how you've
described it, your problem appears to be ambient room
temperature and/or a lack of airflow on the CPU.

BTW if your PS is hot to the touch for extended periods
it won't last very long.

Re: Lowering PC temp

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My thought was if I move the PS outside of the CPU case there wouldn't be as
much heat buildup inside. The fans are sucking from the room, not inside of
the wall where everything vents so I dont think much 'hot' air would
backflow into the computer.

Re: Lowering PC temp

Immediately stop using your computer until you get proper ventilation.  If
your power supply is 'quite hot to the touch'.  If the outside of your power
supply is that hot, components inside are at way to high a temperature.  The
capicators will fail quickly, at the best.  And the temperature inside your
system case should be only a few degrees C higher than the room temperature.
You may, however be measuring the motherboard temperature, and that
temperatuer, with proper ventilation should be kept to less than 10 degrees
C above room temperature.

Your first problem seems, from your description, is that you have almost no
case ventillation at all.  The space between studs in an interior sheet-rock
wall has no real connection to any other space.  Essentially you are just
blowing into a closed space about 18 inches by 8 or 9 feet, and computer
cooling fans will not work at all against the back pressure of trying to
blow up a rigid balloon.

And you really should not try extending your power supply cables and placing
the power supply outside the system case - there are questions of safety,
Radio Frequency Interference, and poor regulation caused by the extra
inductance and voltage drop ( the DC current draw is very high and the
voltages are low.)

You need to ventilate in to open air (in the room) and insure that your fans
are actually circulating air from outside completely through your system
case, and not working against each other.

The outside case of your power supply should be only a few degrees above the
temperature of the room air, IF your fans are properly installed and

Phil Weldon

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Re: Lowering PC temp

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Thanks for your post. I was afraid that I might have some of the problems
that you mentioned in regard to extending the PS externally. I am not sure
whether the issue of venting into the sheet rock wall is really a issue as
it only increases my temp by a few degrees.

I just replied back to Rick, maybe I am over-drawing my PS and that is why
it is heating up so much. When the CPU is idle the PS is barley warm. I am
going to reduce the number of connected components as a  test today and see
what happens.

Will post back. Thanks again.

Re: Lowering PC temp

It would help if you gave a bit more information:
System manufacturer/vendor
how you are measuring temperatures
temperature of the air inside the system case
CPU temperature at idle
a clearer idea of how your fans are placed and the direction of air flow
installed cards, especially the display adapter
installed memory
hard drive sizes  (by the way, even if the hard drives are not in use, they
are still drawning significant power if still spinning)

Your power supply at 180 watts is pretty puny.  It is not possible to
comment on overloading without knowing more of the above, but 180 watts is
probably not adequate.

At any rate, even if the power supply IS overloaded, its contribution to the
heat load of your system would be no more than that from an adequate power

You may neend to replace your power supply with a higher capicaty one (350
Watts or more.)  BUT if your power supply is only 180 Watts, you likely have
a computer built  by a large vendor like DELL, and there may be issues with
a new power supply fitting/connecting.

Phil Weldon

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Re: Lowering PC temp

The PC is home built.
MB is Aaza P4X2-AV with a Via chipset
P4 2Ghz
2 HD (1 internally mounted, the other is a removable HD tray. There is very
a small fan on the HD tray mount)
1 DVDRW Drive
1 CDRW Drive

ATI all in Wonder TV/VGA card (runs a little bit warm)

(All fans are blowing out of case)
Zalman CNPS7700 CPU Cooler
3.5" Venting fan on back side of case
PCI Slot fan in PCI slot

The temp I am reporting is with the only temp sensor supported by the MB.
The temp reported in the BIOS is the same as the temp measured while Windows
is idle (measured in Windows with Motherboard Monitor 5). Idle temp about

I should probably go to RS and get a little digital thermometer to measure
temp inside of case. As I mentioned in an earlier post temp can get as high
as 62' after several hours of running BurnMax.

I am going to take your suggestion and look into a higher wattage PS.

In regard to:
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If I am really pushing the PS and it cant handle the current draw, wouldn't
it be running hotter than a PS that could?

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Re: Lowering PC temp

Your new information puts a whole new light on the situation.

Since only one temperature is reported, that temperature is almost certain
to be the CPU temperature as measured by the CPU on-chip-thermal-diode, not
the case temperature or motherboard temperature.  You should check the
motherboard manual for information on the sensor/sensors provided.  A
temperature of 60 C is a bit high, but not at all out of the operating range
of a Pentium 4 2 GHz.

The relatively high CPU idle temperature indicates that your case
ventilation is inadequate.  The usual slot fan does very little for case
ventilation, having less than 20% of the air flow of a typical 80 mm fan.

Bottom line, now that you have supplied adequate information (except for the
hard drive capacities) -

*your temperatures are not unreasonable (probably not much worse than a
typical Dell Desktop)
*you don't have much in the way of fans
*your power supply is very close to being inadequate, but probably about the
same size Dell would use for a similar system
*don't even THINK about overclocking until you supply adequate case

Phil Weldon

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Thanks for the info. Just bought an RS indoor/outdoor thermometer to measure
room temp vs. inside of case temp. Will post results.

I am going to research PS as suggested in one of the posts (if my wife would
stop making me take walks out on beautiful days I might have gotten
some"work" done this weekend).

What would you recommend for fans, I cant think of another place to add one.

You say that I am well within the operating range of a P4 2 GHz. I thought
the max temp was about 70' and I can hit 63'. Am I wrong about the max temp?
Isn't this cutting it a bit close (it isn't even a hot summer day ambient
room temp could be 10-20' hotter in the summer)

BTW:  HD are 40GB & 80GB IDE (Seagate Barracuda ATA IV/Maxtor 6Y080l0 ATA


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Re: Lowering PC temp

You can get information on Intel CPUs at
http://support.intel.com/support/processors/index.htm .
Depending on whether your CPU is a 473-pin (256 Kbyte L2 cache, 0.18 micron)
or a 478-pin (512 Kbyte L2 cache, 0.13 micron) product, the thermal spec
will be around 75 C or 69 C.

You really need to use some of this information to research answers for
yourself.  It still seems to me that your air circulation is inadequate, and
that exhausting into a slot in an interior wall is a bad idea.

Since nothing has actually gone wrong, and since your system may not be
worth upgrading without replacing everything but the drives, I suggest
leaving it the way it is except for exhausting the warm air into the room.
Don't spend any more money on incremental improvements.

I assume you are not a big 3D game player, so you are unlikely to produce
anything near the temperature levels you get in CPU burn from normal
operation.  Leave your system alone unless it begins to crash.  You can't
destroy an Intel CPU by overheating; it will automatically shut down before
damage occurs, and long before that point the system will have already
crashed, and the CPU will have begun to cool off.

If your CPU is a 473-pin (256 Kbyte L2 cache, 0.18 micron) CPU, it has
essentially NO overclocking potential.

One more thing you can do, if the air temperature entering the CPU heatsink
is reasonably cool (say, less than 5 C or so above room temperature, check
the installation of the heatsink/fan; the thermal compound may have dried
out.  BUT, don't do this unless you do more research on HOW.  It really
isn't worth the trouble if you are not having problems with your system.

Any new system you build will definitely need a power supply with at least
twice the capacity of your present system, so if you might junk the present
system, it might be a good idea to get a 350 Watt or 450 Watt ATX12V
powersupply for $50 to $100 US.  If you are not familiar with this
suggestions, I'd suggest you just keep things as they are except for the
exhast location.

****"If it ain't broken, don't fix it" is a pretty good rule to follow
unless you want to learn, and are willing to spend the time and money to
recover from mistakes.

Finally, just for an example - my system most comparable to yours is
CPU  Pentium 4 1.6 GHz Northwood ( 512 Kbyte L2 cache, 0.13 micron) @ 2.4
GHz with the stock Intel heatsink/fan
640 MByte RDRAM
Intel 850 chipset
case ventilation:
     two 80 mm fans exhausting out through the rear panel
     one 120 mm fan blowing air in onto the
     two 80 mm fans (in-line) exhausting out the rear of the case
temperature:  for 28 C ambient room temperature, 48 C CPU temperature using
the CPU burn function in SiSoft Sandra.

As you can see, this older system isn't really worth upgrading unless the
CPU, motherboard, and memory were replaced at the same time.

Phil Weldon

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Thus you have a cabinet ambient temperature.
o Ideally cabinet-ambient temp = room-ambient temp
o Achieved via cabinet intake & exhaust venting &/or fans

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Cabinet venting fan...
o Fan set to exhaust air & be located at the cabinet top
---- alternatively intake air & be located at the bottom
o Another airflow port is required to feed this
---- eg, cabinet exhaust fan requires a cabinet intake vent
o The fan needs to be sized sufficiently for the PC
---- 300cfm cools 1500W *before* considering airflow resistance
-------- crude check (doesn't consider Watts, airflow-mass & temp delta)
---- typical PC dissipates 250W re PC + PSU inefficiency
-------- so you need 250/1500 * 300 = 50cfm

I suspect:
o Your cabinet fan moves nothing like 50cfm
---- application requires a 120mm fan or twin 92mm fans
o Your 12"x12" hole in the sheetrock may be just a hole
---- wall void itself may be sealed re basic fire blocking
---- alternatively it may be all that stops your PC overheating

The PSU is running too hot if it is hot to the touch.
o Suggests the PC is recirculating its own air (re cabinet)
o Alternatively the cabinet is not having enough air changes

Nothing wrong with putting a PC in a cabinet.
o The cabinet must have sufficient air changes per hour
o Effectively such that cabinet-ambient = room-ambient

I would not move the PSU outside the cabinet, messy and
may merely introduce more problems that it solves.

You just need to verify the above points...
1) cabinet has a sizeable inlet to the room or intake fan
2) cabinet has a sizeable exhaust to the room or exhaust fan
3) wall void may be beneficial or detrimental in this system

If the fan is sufficiently large, check the intake/exhaust sizing.
Fit a PC into a cabinet & you must manage cabinet-ambient.

ATX specification requires failure to be contained without an
excess discharge of smoke or other materials, solids, anti-matter.
However some PSUs fail ATX specs, wall voids in theory may
propograte ugliness to somewhere it isn't desireable/known.

The PSU may be overloaded - however it is quite possible to
run a P4 PC with a 180-200W PSU - small form factors often do.
Dorothy Bradbury
www.dorothybradbury.co.uk for quiet Panaflo fans

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