Cooling Questions

[Spajky]

36gig WD Raptor

how many points you get with Sandra Disk bench?
(just curious)

-- Regards, SPAJKY
& visit - http://www.spajky.iscyber.com
Celly-III OC-ed,"Tualatin on BX-Slot1-MoBo!"
E-mail AntiSpam: remove ##

 

[David Maynard]

Nope, Gateway, Compaq and others have been using passive coolers and
ducts since the Pentium 1 days.

True. Different designs, however.

The CPU runs hotter as a result,
then and today.

Not so. It is not 'because' of the ducted design. It because their design goal,
regardless of the chosen cooling method, is proper operation within the
temperature specs and not 'the coolest we can get it'.

Ductwork is merely cheaper than a high-quality
heatsink,

Again, not necessarily so. Depends on the overall design.

which would keep the CPU cooler AND be as quiet.

Simply not possible. HSF assembly gets it's air from and discharges it's hot air
into the case, which then needs to be ventilated more than if that hot air were
immediately expelled (as it is in the ducted design). The result is more fans
(or fan speeds) and more noise for the equivalent cooling.

The other
benefit is that these systems are being shipped, sometimes great
distances under less-than-ideal conditions, so reduced heatsink weight
as on the Dells is reducing the chance of RMA due to socket or CPU
damage.

Odds are the 'passive' (it's not really passive; the fan is just located
differently) heatsink is as massive, perhaps more, than one with the fan mounted
on it. It depends on the design if removal of the fan compensates but it isn't a
foregone conclusion.

Proper fan selection is crucial to achieve low noise on an active
heatsink, but so it was also when Dell built their ducted system.

True. The point is, by ducting the hot CPU air directly out of the case, rather
than mixing it in as a HS mounted one does, there is less work needed to cool
the system.

 

[lhorwinkle]

I agree. Why do people pay good money for an expensive product, then allow
an in-warranty defect to befuddle them. I assume this is a new box (the 8300
hasn't been around long). So if it's in warranty, let Dell sort it out (or
take it back!).

Anyway, 60-70 C is frying hot. (That's 140-158 F for us Americans). Normal
temps run in the mid- to high-30s. Something is very wrong.

 

[127.0.0.1]

It really makes you wonder if this guy thinks that Dell is "cutting costs"
by engineering new cooling solutions for each new system they come out with.

A duct cooling system involves a custom heatsink, and a custom duct housing
which has to be changed for every new system model. I would think that just
plonking a decent CPU "HS/fan" type cooler on there would be much easier,
and cheaper. Why then re-invent the wheel with each new model?

Obviously ... because it WORKS BETTER!

Get a clue 127!

And TC, thank you for saying what I had been itching to since the first
ignorant post I saw from this guy.


Drumguy

stay on topic please.
Original Poster (OP) needs help with his overheating problem, not a debate
on how well dell designs their mass produced products. Drumguy still has yet
to post a solution.
i gave my suggestion on adding a new Heat Sink (HS) + fan. what has Drumguy
suggest? leave it alone because it shouldn't be overheating? that's not a
solution.

i'm not the type to lecture someone who needs help. if i can fix it, then i
will. will i teach that person the physics involved in locating the cause of
the problem? not for free.

i may be ignorant, but at least i'm polite.
my last post on this thread...

 

[kony]

True. Different designs, however.


Not so. It is not 'because' of the ducted design. It because their design goal,
regardless of the chosen cooling method, is proper operation within the
temperature specs and not 'the coolest we can get it'.

The issue is not one of achieving "the coolest we can get it", but
rather noise/heat ratio, that a duct impedes exhaust, making the rear
fan noiser at the same exhaust flow rate. To keep the CPU at the same
(high) operating temp as in the Dell ducted system, a good active
cooler's fan can run at low enough RPM, low enough turbulence, that
what litte noise it creates, being buffered by the enclosure, is less
audible than the increase in ducted exhaust fan noise. Running the
rear fan at higher RPM is necessitated by the duct, else there is more
heat buildup in the system.

The total system heat generation can be considered constant so the
total airflow through the system must also remain the same else the
Dell system runs hotter in more areas than just the CPU. Lower air
intake into the system will then result in hotter air entering the
heatsink.

Proper operation within the temperature spec (instead of lowest
possible CPU temp) is the notion that allows using a low-RPM fan on
the heatsink instead of the noisey fans most people compare to the
Dell ducted system. If we are considering a custom-designed OEM
cooling system it has to be compared to an active cooling stategy with
similar forethought, not just a cheap/junk $5 'sink with a
tornado-speed fan on top.

Again, not necessarily so. Depends on the overall design.

There are a lot of variables involved with design, production, parts,
but in general a high-volume production piece of plastic should be
less costly than a second fan and more elaborate heatsink. There can
be exceptions but practically we can only consider the ducted systems
being used by OEMs, not theorectical, nonexistant systems. A ducted
cooling system does tend to be the best noise/heat ratio if there are
budget constraints, at least for an OEM who can buy in bulk.

In other words, it can be the best budget-optimized solution for an
OEM, but optimizing as much as possible for cooling or noise, a ducted
passive 'sink cooling system cannot attain as low a noise/heat ratio.
Combining the two strategies, having a duct AND an active cooler,
would be the choice for lowest temps but again the duct necessitates
an increase in noise else *something* will run hotter, and of course
it will tend to be the most expensive alternative.

Simply not possible. HSF assembly gets it's air from and discharges it's hot air
into the case, which then needs to be ventilated more than if that hot air were
immediately expelled (as it is in the ducted design). The result is more fans
(or fan speeds) and more noise for the equivalent cooling.

It is possible with a high-quality active cooler. Even though some
heated air is recirculated the primary source of audible noise in an
optimized configuration is the rear fan, which is less efficient with
a duct on it. By optimizing both methods there might be similar
noise/heat ratios, but then the ducted system is more dependent on
preservation of the chassis airflow model.

Odds are the 'passive' (it's not really passive; the fan is just located
differently) heatsink is as massive, perhaps more, than one with the fan mounted
on it. It depends on the design if removal of the fan compensates but it isn't a
foregone conclusion.

Passive 'sinks are usually less densely populated with fins and have a
greater percentage of weight at their base, which is less leveraged
force against the socket or retention mechanism.

True. The point is, by ducting the hot CPU air directly out of the case, rather
than mixing it in as a HS mounted one does, there is less work needed to cool
the system.

Possibly, not not necessarily, and work is not always directly related
to _audible_ noise. Increasing the work done by a single fan by
having it create a suction through a duct, requires higher RPM, enough
so that the fan is no longer as quiet as the audible sum of [that fan
at lower RPM & turbulence, same airflow rate without duct] + [fan on
heatsink keeping CPU at same temp].

We could argue that a highly optimized (per system) duct be used, but
it would then need be compared to an optimized active 'sink, and the
optimized duct would be even less forgiving of user modifications to
the system, which must be considered on a PC.


Dave

 

[Lester Horwinkle]

Well, I now own 5 Dells at home with that "bad design".

Where I work, there are about 2500 more of them.

This "bad design" has not caused problems.

 

[David Maynard]

The issue is not one of achieving "the coolest we can get it", but
rather noise/heat ratio, that a duct impedes exhaust, making the rear
fan noiser at the same exhaust flow rate. To keep the CPU at the same
(high) operating temp as in the Dell ducted system, a good active
cooler's fan can run at low enough RPM, low enough turbulence, that
what litte noise it creates, being buffered by the enclosure, is less
audible than the increase in ducted exhaust fan noise. Running the
rear fan at higher RPM is necessitated by the duct, else there is more
heat buildup in the system.

Nice theory but not true. Case temp is cooler because the heat is directly
exhausted rather than circulated. You also fail to take into account that the
Dell motherboard is designed with the CPU socket located to minimize duct air
impedance.

The total system heat generation can be considered constant so the
total airflow through the system must also remain the same else the
Dell system runs hotter in more areas than just the CPU.

Directly exhausting the heat requires less airflow than first mixing it then
exhausting it. Plus it results in cooler air into the heatsink because the case
air is cooler: not being first preheated with the heatsink exhaust.

Lower air
intake into the system will then result in hotter air entering the
heatsink.

There isn't necessarily lower air intake into the system but it could be as it's
easier to cool the remaining components when you don't have the CPU heat being
vented into the case.

Proper operation within the temperature spec (instead of lowest
possible CPU temp) is the notion that allows using a low-RPM fan on
the heatsink instead of the noisey fans most people compare to the
Dell ducted system.

True, but no fan is still less noise than a 'low noise' fan.

If we are considering a custom-designed OEM
cooling system it has to be compared to an active cooling stategy with
similar forethought, not just a cheap/junk $5 'sink with a
tornado-speed fan on top.

No fan is still less noise than a 'low noise' fan and, with your active HSF, you
STILL need the case fan; with more airflow because it has more volume to get rid of.

There are a lot of variables involved with design, production, parts,
but in general a high-volume production piece of plastic should be
less costly than a second fan and more elaborate heatsink.

It's your assumption than an active heatsink is necessarily "more elaborate" for
the same cooling that I dispute.

There can
be exceptions but practically we can only consider the ducted systems
being used by OEMs, not theorectical, nonexistant systems. A ducted
cooling system does tend to be the best noise/heat ratio if there are
budget constraints, at least for an OEM who can buy in bulk.

It's also the best technical noise/heat solution between the two regardless of
cost. It's simply a more efficient use of the airflow.

In other words, it can be the best budget-optimized solution for an
OEM, but optimizing as much as possible for cooling or noise, a ducted
passive 'sink cooling system cannot attain as low a noise/heat ratio.

I have no idea what makes you think that simply recirculating hot CPU air inside
the case, rather than expelling it, is 'better'.

Ducting CPU heat out is inherently a better cooling/noise solution.

Combining the two strategies, having a duct AND an active cooler,
would be the choice for lowest temps but again the duct necessitates
an increase in noise else *something* will run hotter, and of course
it will tend to be the most expensive alternative.

You simply refuse to recognize the benefit of expelling the heat directly rather
than first mixing it with case air and then having to expel the entire case
volume to remove it. You don't NEED the same airflow to remove the heat if it
goes directly out.

Not to mention one can use larger, quieter, fans on the rear mount than can be
shoved into the socket footprint.

It is possible with a high-quality active cooler.

I don't care HOW 'quality' your active cooler is; it's still dissipating the CPU
heat INTO the case and not OUT of the case. And after you've dumped the CPU heat
into the case with an active HSF you STILL have to have a case fan to expel it.

Even though some
heated air is recirculated the primary source of audible noise in an
optimized configuration is the rear fan, which is less efficient with
a duct on it.

You have to expel the heat sooner or later and it takes less airflow if the CPU
heat is vented directly instead of having to expel the entire case volume to get
rid of it.

By optimizing both methods there might be similar
noise/heat ratios, but then the ducted system is more dependent on
preservation of the chassis airflow model.

'Preserving' the 'chassis airflow model'? What then heck does that mean? The
chassis has to be ventilated regardless. MORE so if you dump the CPU heat into it.

Passive 'sinks are usually less densely populated with fins and have a
greater percentage of weight at their base, which is less leveraged
force against the socket or retention mechanism.

Whether true or not it's not a passive heatsink. The fan is just located in a
different spot.

True. The point is, by ducting the hot CPU air directly out of the case, rather
than mixing it in as a HS mounted one does, there is less work needed to cool
the system.

Possibly, not not necessarily, and work is not always directly related
to _audible_ noise. Increasing the work done by a single fan by
having it create a suction through a duct, requires higher RPM, enough
so that the fan is no longer as quiet as the audible sum of [that fan
at lower RPM & turbulence, same airflow rate without duct] + [fan on
heatsink keeping CPU at same temp].

Doesn't need the same airflow over the CPU heatsink as the heatsink is operating
with cooler case air, since it's not preheated with the exhaust from the CPU.
Plus it's venting the case in addition to whatever case cooling you'd require
when dumping CPU heat into the case.

We could argue that a highly optimized (per system) duct be used, but
it would then need be compared to an optimized active 'sink, and the
optimized duct would be even less forgiving of user modifications to
the system, which must be considered on a PC.

"Optimized" is precisely what an active HSF is not. It's the 'norm' for generic
systems because one cannot make any assumptions about the system design: I.E.
what else is in it and where anything is located. You can't count on there even
being a rear exhaust port or, if it exists, that it's located where a 'standard'
duct (that doesn't exist) would lead to, not to mention you don't know the exact
location of the socket as that is left open, within reason, to the motherboard
designer. But you CAN just slap an active HSF on it and then leave case cooling
to someone else; with the typical solution being to slap gaggles of fans
everywhere to 'cool' it.

 

[drumguy1384]

stay on topic please.
Original Poster (OP) needs help with his overheating problem, not a debate
on how well dell designs their mass produced products. Drumguy still has yet
to post a solution.
i gave my suggestion on adding a new Heat Sink (HS) + fan. what has Drumguy
suggest? leave it alone because it shouldn't be overheating? that's not a
solution.

i'm not the type to lecture someone who needs help. if i can fix it, then i
will. will i teach that person the physics involved in locating the cause of
the problem? not for free.

i may be ignorant, but at least i'm polite.
my last post on this thread...

Hey man, don't get me wrong. I'm not saying that a new cooling solution
isn't what he needs ... but you said that the duct system is inferior in
design to a conventional HS/Fan solution. I was merely disagreeing with you.

I was not attempting to solve the OTP's problem ... only to take issue with
your insinuations about the effectiveness of a duct cooler. But, since you
insinuate that because I didn't tell him what I would do that I don't have a
solution I'll get to it shortly.

Shall I quote you?

"thats a poor design."

"having no fan on a cpu HS is not a good design. i'd rather see the dell
executives cut their bonuses to save on cost than skimping out on proper cpu
cooling."

That's pretty inflammatory language there ... and hardly polite. I was
simply pointing out that you are wrong to say that a duct cooling system is
worse than a traditional HS/Fan solution.

Sure, there are many aftermarket coolers that will do a better job of
cooling his CPU ... but unless you find one with a 120mm fan (as his duct
fan is) anything he get's will be louder. Of course I agree that a bit
louder and stable is better than quiet and unstable.

But his heat problem may be easily curable by blowing any dust out of the
heatsink fins and/or re-applying it using some high quality thermal paste,
such as Arctic Silver III. It may also be that the fan in his duct system is
crapping out ... which can and does happen, especially if it's left on all
the time. In which case, if it can't be replaced independently of the duct,
it'd be best to remove the duct system and use a conventional cooler and
another quiet 120mm case fan in the back without the housing. However, if
the fan is the culprit and it's not permanently affixed to the duct then the
best course of action would be to replace it with another 120mm fan and
leave the duct in place.

The truth is that this cooling solution works just fine in every system it's
used in ... and it wouldn't continue to be used it if didn't work. Either
it's crammed up with dust or the fan is crapping out. Simple as that.

Your first course of action was to can the whole cooling system and replace
it with a louder conventional system ... because it was, in your opinion, "a
poor design." I just submit that may not be necessary, and that he may do
better to try and salvage what he's got. He would end up with an adequate
cooling system that is as quiet as it's ever been, and keeps his CPU quite
cool enough.

Good enough for ya?


Drumguy

 

[kony]

Nice theory but not true. Case temp is cooler because the heat is directly
exhausted rather than circulated. You also fail to take into account that the
Dell motherboard is designed with the CPU socket located to minimize duct air
impedance.

Anyone with a Dell system can open their system, feel the heatsink,
and know that it is true. The CPU socket location does minimize the
impact, but that impact is still a great reduction in airflow.
Reduced airflow results in higher heat retention, there's no fancy
combination of ducting theories that changes that. I'm not
suggesting that Dell systems usually run hot enough to be instable,
but neither do other equally thought out, quiet systems.

Directly exhausting the heat requires less airflow than first mixing it then
exhausting it.

Yet there is less airflow, significantly less going though the
heatsink, enough less that even a percentage of recirculated air on an
active cooler keeps the CPU at lower temp. The goal is not to reduce
airflow, to get the maximual cooling benefit from each CFM of airflow,
or rather it shouldn't be. The goal should be maximal cooling benefit
from each db of noise, and give the system tolerance to user
alteration, component additions, etc.

Plus it results in cooler air into the heatsink because the case
air is cooler: not being first preheated with the heatsink exhaust.

Reduction in intake airflow (if the ducted system is operating with
rear fan at same noise level) causes the air to become more heated on
it's way to the duct. Heat can't magically escape... given a
radiation rate the airflow rate dictates total heat retention over
ambient external room temp. No matter how great the duct is, it
reduces airflow, which increases heat retention.

There isn't necessarily lower air intake into the system but it could be as it's
easier to cool the remaining components when you don't have the CPU heat being
vented into the case.

There IS necessarily lower air intake. It is impossible to add a duct
to the rear fan and have the same exhaust rate, same intake rate as
before it's addition, unless the fan is operated at higher RPM, which
is louder, and of course increases airflow on the ductless system
further.

True, but no fan is still less noise than a 'low noise' fan.

Not true from a user's perspective. Fans mounted on the chassis allow
a far greater percentage of sound to escape the chassis. The increase
in rear fan noise to attain same airflow as a ductless cooling system,
is audibly lower to the user than the heatsink fan running at low RPM.

No fan is still less noise than a 'low noise' fan and, with your active HSF, you
STILL need the case fan; with more airflow because it has more volume to get rid of.

Noise is not additive, two lower RPM fans are usually quieter than one
higher RPM fan, particularly when the higher RPM fan is mounted on the
wall of the chassis, and even further the higher-pitch of the
higher-RPM rear fan is more noticeable to human ears. I will mention
again that proper fan selection is crucial.

It's your assumption than an active heatsink is necessarily "more elaborate" for
the same cooling that I dispute.

I could likewise dispute that a passive cooler is more elaborate than
an equally well-designed active cooler. Actually I feel the opposite,
that it takes a much more elaborate and expensive passive cooler to
come anywhere near the cooling efficiency of a cheap, low-end active
cooler. The problem is, they generally aren't more elaborate when
comparing to a good active cooler, not mid-to-low end.

Which should cost more to produce in volume? Granted there are some
really junky fans that may hardly be worth the plastic they're made
out of from a reliability or noise standpoint, but instead considering
a fan of similar quality to the rear fan, the main issue would be
volume production. Since fans are already produced in volume,
production lines are in place to produce them regardless of what Dell
is doing. If Dell buys enough ducts they're going to be even more
inexpensive, and since these are likley supplied by the case
manufacturer it may be a "free" duct. I don't recall any case
manufacturers providing free heatsink fans ecxept in rare cases like
thoose miniature Shuttle systems or similar where space constraints
make a specific heatsink size necessary.

It's also the best technical noise/heat solution between the two regardless of
cost. It's simply a more efficient use of the airflow.

A ducted passive cooling system is a more efficient use of a given
CFM, but it's not like there's only "X" amount of airflow allowed,
rather the primary issue is usually noise. Introducing the duct
causes a significantly lower CFM to noise ratio. It's unavoidable
with an axial fan.

I have no idea what makes you think that simply recirculating hot CPU air inside
the case, rather than expelling it, is 'better'.

Recirculating airflow isn't better than not recirculating, but since
that's not the only issue it has to be weighed against others, like
total airflow, and a greater airflow though the CPU 'sink. The
greater the airflow though the CPU 'sink on a passive cooler (given an
optimal duct for that purpose) the greater the reduction in exhaust,
and intake airflow. Moving the opposite direction, reducing
backpressue by diverting less air through the CPU 'sink will somewhat
increase chassis airflow, but the CPU runs hotter.

Ducting CPU heat out is inherently a better cooling/noise solution.


You simply refuse to recognize the benefit of expelling the heat directly rather
than first mixing it with case air and then having to expel the entire case
volume to remove it. You don't NEED the same airflow to remove the heat if it
goes directly out.

At the same airflow rate it is of benefit to remove the heated air as
directly as possible. At a greater airflow rate the benefit of it is
quickly overcome. Higher exhaust rate also reduces mixing of heated
air, reduces the pre-heating of air from other components prior to
reaching the CPU heatsink.

Not to mention one can use larger, quieter, fans on the rear mount than can be
shoved into the socket footprint.

The size of rear fan is a constant, since the same chassis can be used
for either cooling configuration. Given this same sized fan, it will
produce more noise at same flow rate OR same noise at lower flow rate
with a duct on it.

A fan mounted on the CPU heatsink need not be as large as the case
fan, will move a lot more air through the heatsink due to proximity,
because axial fans cannot create significant pressure.

I don't care HOW 'quality' your active cooler is;

Perhaps this is why you haven't seen the same results. Passive
coolers don't even come close, not with a duct, not with a 120mm fan.
They usually provide just enough margin to operate stabily, little
more than that.

it's still dissipating the CPU
heat INTO the case and not OUT of the case.

A great portion of the CPU exhaust from an active cooler is directly
removed, especially with a 120mm fan.

And after you've dumped the CPU heat
into the case with an active HSF you STILL have to have a case fan to expel it.

So you don't really care about performance, you're just opposed to
using two fans?

You have to expel the heat sooner or later and it takes less airflow if the CPU
heat is vented directly instead of having to expel the entire case volume to get
rid of it.

The system 'creates' a given amount of heat. There is no duct that
changes that. The lower the exhaust rate, the hotter the air is...
nothing changes that either. The ducted system has lower exhaust
rate at same noise level, because of the duct... exactly what this
duct does, concentrate and redirect airflow, is exactly why it reduces
airflow. It can't be argued that all this air was heated passing
through the heatsink on it's way out because with less cool intake air
the rest of the components are hotter, heat the intake air more. Many
such ducted systems even feel noticably warm on the outside, a clear
indication that ambient temps are quite high.

'Preserving' the 'chassis airflow model'? What then heck does that mean? The
chassis has to be ventilated regardless. MORE so if you dump the CPU heat into it.

Dell (and others) have to move a cetain amount of airflow through that
CPU heatsink, and likewise in other areas of the chassis. At a bare
minimum I'll bet they want it to last until the warranty is expired.
This is an engineered cooling system to achieve the desired result,
not just the duct but the whole chassis... The proposed solution is
an environmental model of an actual system, before it ever goes into
production. If the intake, exhaust, or flow pattern is altered, the
target temps deviate from the model. Our OP, Peter, may be
experiencing exactly that when he added the exhaust fan for his video
card, which reduces exhaust though the duct even further. He might
see improvement by using an intake fan, except that I dont' recall
seeing any slot-mounted intake fans, but if there are any...

Whether true or not it's not a passive heatsink. The fan is just located in a
different spot.

Yes, but it goes to the point of stress against the socket, retention
mechanism, or CPU during shipping... just another motivation for Dell
to use this passive 'sink design.

Doesn't need the same airflow over the CPU heatsink as the heatsink is operating
with cooler case air, since it's not preheated with the exhaust from the CPU.
Plus it's venting the case in addition to whatever case cooling you'd require
when dumping CPU heat into the case.

It doesn't need as much airflow given a 'sink of same efficiency,
which is another issue that could expand this discussion into
something more fit for a book rather than a newsgroup thread.
Historically and today, passively cooled CPUs run hotter, even though
they (all, AFAIK) use a duct. To many people this is considered
common knowledge. Dumping CPU heat into the case with an active
cooler isn't an issue of the significance that you suggest, since the
airflow is moving in one direction, up and out of the case. Some
heated air is mixed and recirculated though the heatsink but the
airflow rate is SO much greater than even slightly warmer air results
in a lower CPU temp.

"Optimized" is precisely what an active HSF is not.

On the contrary, it is optimized to cool the CPU, the exact goal.
When a high quality sink is paired with a low-RPM fan, it is then
futher optimized to have maximum cooling with minimum noise.

It's the 'norm' for generic
systems because one cannot make any assumptions about the system design: I.E.
what else is in it and where anything is located.

It has widespread adoption because it works well in comparision to the
alternatives of similar cost.

You can't count on there even
being a rear exhaust port or, if it exists, that it's located where a 'standard'
duct (that doesn't exist) would lead to, not to mention you don't know the exact
location of the socket as that is left open, within reason, to the motherboard
designer.

Yes, the active 'sink works SO well that it can overcome all these
obstacles most of the time. Not because it's "generic" but becuase it
has such a huge margin over minimal efficiency required, that when a
decent chassis is used the active sink works even better, even with a
silent fan on it.

But you CAN just slap an active HSF on it and then leave case cooling
to someone else; with the typical solution being to slap gaggles of fans
everywhere to 'cool' it.

It's true enough that some people purchase, build, redesign, and
outfit their systems in ignorance, but it has little to do with this
topic since these same folks could either improve or degrade a ducted
passive CPU cooling system using the same methods as on one actively
cooled. We both know there are plenty of crap cases out there too,
but that's not an argument towards a ducted cooling system, but rather
to choose the case carefully regardless of which cooling system will
be used.

It's usually the situation that user mods to a passively cooled system
have a greater impact, positive or negative, depending on where the
fan is located and whether it's intake or exhaust.

I suppose we just won't come to an agreement... it happens.
I do despise long threads so if you want a thread where we can all
argue about passive/ducted vs active cooling instead of hijacking
Peter's thread, that's fine, but I'm done with this thread.


Dave

 

[127.0.0.1]

then cause

Hey man, don't get me wrong. I'm not saying that a new cooling solution
isn't what he needs ... but you said that the duct system is inferior in
design to a conventional HS/Fan solution. I was merely disagreeing with you.

I was not attempting to solve the OTP's problem ... only to take issue with
your insinuations about the effectiveness of a duct cooler. But, since you
insinuate that because I didn't tell him what I would do that I don't have a
solution I'll get to it shortly.

Shall I quote you?

"thats a poor design."

i guess that wasn't my last post...
i still hold to my statement. i was being brief and to the point. dell's
models aren't designed individually. err, i should go even further and say
that dell doesn't design computer systems at all. they purchase existing
systems that will make them money. i will stop here about poor designs.

"having no fan on a cpu HS is not a good design. i'd rather see the dell
executives cut their bonuses to save on cost than skimping out on proper cpu

That's pretty inflammatory language there ... and hardly polite.

if i wasn't polite...

I was
simply pointing out that you are wrong to say that a duct cooling system is
worse than a traditional HS/Fan solution.

not completely inflammatory. i was laid off in product development at lucent
bell labs, thanks to the executive's cost cutting strategies. if i still had
access, i can show you thermal data on that dell design compared to mac's.
but with no data at hand, i'm just going to offer the client a simple
solution. put a fan on the cpu.

Sure, there are many aftermarket coolers that will do a better job of
cooling his CPU ... but unless you find one with a 120mm fan (as his duct
fan is) anything he get's will be louder. Of course I agree that a bit
louder and stable is better than quiet and unstable.

client didn't mention noise being a problem.

But his heat problem may be easily curable by blowing any dust out of the
heatsink fins and/or re-applying it using some high quality thermal paste,
such as Arctic Silver III. It may also be that the fan in his duct system is
crapping out ... which can and does happen, especially if it's left on all
the time. In which case, if it can't be replaced independently of the duct,
it'd be best to remove the duct system and use a conventional cooler and
another quiet 120mm case fan in the back without the housing. However, if
the fan is the culprit and it's not permanently affixed to the duct then the
best course of action would be to replace it with another 120mm fan and
leave the duct in place.

if it was a $10,000.oo server, then yes, i would find out the cause of the
overheating. but considering the clients level of expertise and the value of
his pc, i would still recommend adding a fan on the HS.

The truth is that this cooling solution works just fine in every system it's
used in ... and it wouldn't continue to be used it if didn't work. Either
it's crammed up with dust or the fan is crapping out. Simple as that.

we aren't dealing with every system, this is a single client with a problem.
a poor design doesn't mean it doesn't work. there are too many examples of
poorly designed equipment to list that we use every day. the first design
flaw, dust gets into the system. a good design will prevent any dust getting
in. the next design flaw, heat generation. why even spend the money on
removing massive heat from the case when there's good development that was
canned which reduced processor heat. the intel processor itself is the main
design flaw. i can go on forever about poor design that is acceptable.
there's a difference between poor design and faulty design.

Your first course of action was to can the whole cooling system and replace
it with a louder conventional system ... because it was, in your opinion, "a
poor design." I just submit that may not be necessary, and that he may do
better to try and salvage what he's got. He would end up with an adequate
cooling system that is as quiet as it's ever been, and keeps his CPU quite
cool enough.

your recommendation is to check the duct effeciency and checking the fan.
with what test equipment? and what specs to compare it with? common sense
dictates that dust should be blown off whenever seen. your final
recommendation is what i stated earlier. put a fan on the HS. if that solves
it, then testing the duct effeciency and fan resistance was a waste of time.
not sure why you keep bringing up the fan noise as being a problem. the OP
has no complaints about that matter.

Good enough for ya?

seems like you are more concerned about winning an arguement then helping
out the OP.

 

[James Lincoln]

I agree. Why do people pay good money for an expensive product, then allow
an in-warranty defect to befuddle them. I assume this is a new box (the 8300
hasn't been around long). So if it's in warranty, let Dell sort it out (or
take it back!).

Anyway, 60-70 C is frying hot. (That's 140-158 F for us Americans). Normal
temps run in the mid- to high-30s. Something is very wrong.

A word of warning, if you do decide to rehouse your system in a new case I
think that you will need to maintain the old PSU. I think (probably wrong!)
that the mobos Dell use are matched to the PSU, so if you change the PSU it
may fry your chipset and board. I think i remember someone saying that they
had replaced the PSU on theirs with another and it knackered their system.

 

[~misfit~]

A word of warning, if you do decide to rehouse your system in a new case I
think that you will need to maintain the old PSU. I think (probably wrong!)
that the mobos Dell use are matched to the PSU, so if you change the PSU it
may fry your chipset and board. I think i remember someone saying that they
had replaced the PSU on theirs with another and it knackered their system.

That is also my understanding. Dell use a standard ATX mobo connector but
with non-standard wiring.

 

[drumguy1384]

not have

i guess that wasn't my last post...
i still hold to my statement. i was being brief and to the point. dell's
models aren't designed individually. err, i should go even further and say
that dell doesn't design computer systems at all. they purchase existing
systems that will make them money. i will stop here about poor designs.



if i wasn't polite...


not completely inflammatory. i was laid off in product development at lucent
bell labs, thanks to the executive's cost cutting strategies. if i still had
access, i can show you thermal data on that dell design compared to mac's.
but with no data at hand, i'm just going to offer the client a simple
solution. put a fan on the cpu.


client didn't mention noise being a problem.
system

if it was a $10,000.oo server, then yes, i would find out the cause of the
overheating. but considering the clients level of expertise and the value of
his pc, i would still recommend adding a fan on the HS.


we aren't dealing with every system, this is a single client with a problem.
a poor design doesn't mean it doesn't work. there are too many examples of
poorly designed equipment to list that we use every day. the first design
flaw, dust gets into the system. a good design will prevent any dust getting
in. the next design flaw, heat generation. why even spend the money on
removing massive heat from the case when there's good development that was
canned which reduced processor heat. the intel processor itself is the main
design flaw. i can go on forever about poor design that is acceptable.
there's a difference between poor design and faulty design.
opinion,

your recommendation is to check the duct effeciency and checking the fan.
with what test equipment? and what specs to compare it with? common sense
dictates that dust should be blown off whenever seen. your final
recommendation is what i stated earlier. put a fan on the HS. if that solves
it, then testing the duct effeciency and fan resistance was a waste of time.
not sure why you keep bringing up the fan noise as being a problem. the OP
has no complaints about that matter.


seems like you are more concerned about winning an arguement then helping
out the OP.

Actually, another poster in this thread made some good sense, and brought up
something else that I hadn't noticed. The OP had added an exhaust fan to
cool his video card.

Because the duct cooler requires adherence to a particular air-flow scheme
it's not getting enough air through it. There is only so much air flowing
into the case, and it used to be only divided between the PSU and the duct
fan ... now it's divided by 3, and who knows what percentage that new third
fan is pulling.

In this case, I will concede my point, and bow to your superior intellect.
Because in this case your original solution is, in fact, the only way to go.

BTW, I am less concerned about winning an argument than I am about knowing
the truth, and being right. So, if I must admit defeat to be right ... so be
it. However, if I believe that I AM right, as in the ducted vs. HS/Fan
debate (which the more I read the less sure I become about which is
superior) then I will most certainly defend myself.


Drumguy

 

[kony]

That is also my understanding. Dell use a standard ATX mobo connector but
with non-standard wiring.

I can confirm that they did do this, but I also recall hearing that
the current systems were using a standard connector, standard wiring.
I suppose to be on the safe side a careful comparision of the OEM PSU
would be needed, though if his current PSU is working and of standard
form-factor there isn't any need to change power supplies.


Dave

 

[Arthur Hagen]

a choice of quieter with overheating vs. a bit noisier with efficient
cooling....
they are still years behind macintosh designs (cube). i forget what the
original processor is. but having no fan on a cpu HS is not a good design.
i'd rather see the dell executives cut their bonuses to save on cost than
skimping out on proper cpu cooling.

Excrement. For a vendor like Dell without brick-and-mortar presence, it's
MORE important to provide good cooling, due to RMAs and returns costing them
a lot more than the average store.
The cooling on the Dell's is, quite frankly, *excellent*, and far surpasses
what the majority of air-based overclockers have. They do have a heat sink
and a fan, and a 120mm fan at that -- they just have the fan placed further
FROM the CPU. What they can do that way is to both *increase* the airflow
(that 120mm fan pushes a LOT more air than your average 60mm whiner),
decrease the noise, and make the case temperature interfere less with the
CPU temperature. You sometimes hear about computers overheating. Tell me
when you last heard about a Dell overheating.

As for your statement "having no fan on a cpu HS is not a good design", it
is laughable. What matters isn't where a fan is placed, or even whether
there is one, but how fast the heat sink can get rid of heat. That can be
accomplished in three major ways -- either increase the flow of the coolant
(better fan/pump, smarter heat sink fin placement), reduce the temperature
of the coolant (heat exchanger, TECs and similar), or increase the thermal
absorbtion of the coolant (usually a higher density coolant, like water
cooling or heavy inert gases).
Based on your statement, a submerged motherboard without a fan is a bad
design, which is just ridiculous.

 

[David Maynard]

Anyone with a Dell system can open their system, feel the heatsink, and know
that it is true.

What they'll 'feel' is that, unless something is amiss, the heatsink is
operating within the design parameters.

The CPU socket location does minimize the impact, but that impact is still a
great reduction in airflow.

Define "great reduction." And while you're at it, compare that to the typical
stamped grill.

Reduced airflow results in higher heat retention,

All else being equal, yes. Thing is, all else is not equal.

there's no fancy combination of ducting theories that changes that.

There's plenty of them. One is increasing the duct size. Another is driving it
with a larger fan.

I'm not suggesting that Dell systems usually run hot enough to be instable,
but neither do other equally thought out, quiet systems.

Actually you were. You suggested his heat problem was due to a "bad design."

Yet there is less airflow, significantly less going though the heatsink,

You make generic statements based on unstated assumptions that are not
necessarily true.

enough less that even a percentage of recirculated air on an active cooler
keeps the CPU at lower temp.

It's not "a percentage." All of it is recalculated into the case.

The goal is not to reduce airflow, to get the maximual cooling benefit from
each CFM of airflow, or rather it shouldn't be.

No one said it was.

The goal should be maximal cooling benefit from each db of noise,

Which ducted systems do.

and give the system tolerance to user alteration, component additions, etc.

And just who decided the system should be infinitely modifiable with 'no
impact'? I'm positive that is not a part of Dell's specification but that the
system working with the expected, and recommended, peripheral additions is.

I suppose you'd argue your car's electrical system is a "bad design" because it
has insufficient "tolerance" to drive an arc welder.

Reduction in intake airflow (if the ducted system is operating with rear fan
at same noise level) causes the air to become more heated on it's way to the
duct.

That would mean it's cooling the other devices in the case better (or else it
couldn't get 'warmer'). So now you've added to your design criteria a "don't
care" about the other device temps?

But your assumption presumes a noisier system because by keeping the 'same rear
fan' you've had to add a fan to the heatsink and any fan, regardless of how
'quiet', has noise.

Heat can't magically escape... given a radiation rate the airflow rate
dictates total heat retention over ambient external room temp. No matter how
great the duct is, it reduces airflow, which increases heat retention.

Your statement is not true because you simply refuse to recognize that ducting
allows the use of different components and that you don't just take the 'cpu
fan' and put it in a duct.

There IS necessarily lower air intake.
Wrong

It is impossible to add a duct to the rear fan and have the same exhaust
rate, same intake rate as before it's addition, unless the fan is operated at
higher RPM, which is louder, and of course increases airflow on the ductless
system further.

Wrong. I simply use a larger diameter fan that I would have otherwise. Or I use
other techniques, like a more efficient exhaust grill.

But I probably don't need to because not having an extra 60 to 90 watts of CPU
heat mixed into the case reduces the airflow I need in the first place.

Not true from a user's perspective.

YEs, it is.

Fans mounted on the chassis allow a far
greater percentage of sound to escape the chassis.

True. But you have to have the rear fan anyway because that heat must still be
expelled. You can either do it efficiently, or compound the matter by first
mixing it with the case volume.

Noise is not additive, two lower RPM fans are usually quieter than one higher
RPM fan, particularly when the higher RPM fan is mounted on the wall of the
chassis, and even further the higher-pitch of the higher-RPM rear fan is more
noticeable to human ears. I will mention again that proper fan selection is
crucial.

You won't HAVE "two lower RPM fans." The rear fan has to run even more air, if
you're first mixing CPU heat into the case volume, to keep case temperature the
same. At the very least it must be the same as "two fans," one being on the
heatsink, does NOT reduce the heat load that must be expelled by the ONE rear fan.

I could likewise dispute that a passive cooler is more elaborate than an
equally well-designed active cooler. Actually I feel the opposite, that it
takes a much more elaborate and expensive passive cooler to come anywhere
near the cooling efficiency of a cheap, low-end active cooler. The problem
is, they generally aren't more elaborate when comparing to a good active
cooler, not mid-to-low end.

It's not worth going into that pile of assumptions when it's not even a passive
cooler in the first place.

Which should cost more to produce in volume? Granted there are some really
junky fans that may hardly be worth the plastic they're made out of from a
reliability or noise standpoint, but instead considering a fan of similar
quality to the rear fan, the main issue would be volume production. Since
fans are already produced in volume, production lines are in place to produce
them regardless of what Dell is doing. If Dell buys enough ducts they're
going to be even more inexpensive, and since these are likley supplied by the
case manufacturer it may be a "free" duct. I don't recall any case
manufacturers providing free heatsink fans ecxept in rare cases like thoose
miniature Shuttle systems or similar where space constraints make a specific
heatsink size necessary.

There's no such thing as 'free'.

A ducted passive cooling system is a more efficient use of a given CFM, but
it's not like there's only "X" amount of airflow allowed, rather the primary
issue is usually noise. Introducing the duct causes a significantly lower
CFM to noise ratio. It's unavoidable with an axial fan.

CFM to noise isn't the ratio of concern either. It's noise for the cooling
needed that is.

Recirculating airflow isn't better than not recirculating, but since that's
not the only issue it has to be weighed against others, like total airflow,
and a greater airflow though the CPU 'sink. The greater the airflow though
the CPU 'sink on a passive cooler (given an optimal duct for that purpose)
the greater the reduction in exhaust, and intake airflow. Moving the
opposite direction, reducing backpressue by diverting less air through the
CPU 'sink will somewhat increase chassis airflow, but the CPU runs hotter.

We're not talking about trying to 'split' the duct airflow between the heatsink
and a case bypass.

At the same airflow rate it is of benefit to remove the heated air as
directly as possible. At a greater airflow rate the benefit of it is quickly
overcome. Higher exhaust rate also reduces mixing of heated air, reduces the
pre-heating of air from other components prior to reaching the CPU heatsink.

Sure. We could just take a wind tunnel fan and suck 500,000 CFM through the case
but that would defeat the noise issue.

The fact is that CPU heat is a major component and directly exhausting it
improves the situation considerably. Which, btw, is why the PSU fan blows
directly outward too.

The size of rear fan is a constant,

Interesting how you keep adding new design criteria as we go along. No, the size
of the rear fan is not a 'constant'.

since the same chassis can be used for
either cooling configuration.

Anything 'can' be used till one adds in the other design criteria, such as cost
(not the only one).

Given this same sized fan, it will produce
more noise at same flow rate OR same noise at lower flow rate with a duct on
it.

Having the same size fan is not a 'given'. Nevertheless, you still don't take
into account that there is less airflow needed since the CPU heat is being
directly exhausted.

A fan mounted on the CPU heatsink need not be as large as the case fan,

To accomplish what? A better statement is it *can't* be as large as the case fan.

will
move a lot more air through the heatsink due to proximity,

Depends on the fan and how fast it turns.

because axial fans
cannot create significant pressure.

If it was 'insignificant' they wouldn't move any air at all. I presume you mean
"a lot" (whatever that is).

Perhaps this is why you haven't seen the same results.

Taking the statement out of context doesn't mean anything.

Passive coolers
don't even come close, not with a duct, not with a 120mm fan. They usually
provide just enough margin to operate stabily, little more than that.

Simply not true. My home made one works fine with an 80mm fan, and it is FAR
from being optimal because I was stuck with where the mobo manufacturer placed
the socket, the case design, and the fan mount.

A great portion of the CPU exhaust from an active cooler is directly removed,
especially with a 120mm fan.

It goes 'in that general direction' but it's still mixed.

So you don't really care about performance, you're just opposed to using two
fans?

That's an illogical leap.

The system 'creates' a given amount of heat. There is no duct that changes
that.
True.

The lower the exhaust rate, the hotter the air is... nothing changes
that either.
True.

The ducted system has lower exhaust rate at same noise level,
because of the duct...

Not true, because the components need not be identical.

exactly what this duct does, concentrate and redirect
airflow, is exactly why it reduces airflow.

If nothing else changed, which is not the situation.

It can't be argued that all this
air was heated passing through the heatsink on it's way out because with less
cool intake air the rest of the components are hotter, heat the intake air
more. Many such ducted systems even feel noticably warm on the outside, a
clear indication that ambient temps are quite high.

Mine doesn't. And the reason 'many' (sic) do is because they're designing to the
operating specifications and not an overclocker's dream of 1C above ambient.

Dell (and others) have to move a cetain amount of airflow through that CPU
heatsink, and likewise in other areas of the chassis.

Everybody has to move a certain amount of air through the chassis.

At a bare minimum I'll
bet they want it to last until the warranty is expired.

They'd be pretty stupid to design it to fail during warrantee.

This is an engineered
cooling system to achieve the desired result, not just the duct but the whole
chassis...
Precisely.

The proposed solution is an environmental model of an actual
system, before it ever goes into production.

Yeah. It's called engineering.

If the intake, exhaust, or
flow pattern is altered, the target temps deviate from the model. Our OP,
Peter, may be experiencing exactly that when he added the exhaust fan for his
video card, which reduces exhaust though the duct even further.

Would be easy enough to test: simply disconnect it and see if CPU temps change
significantly.

Frankly, it's hard to guess when he states his mods are "too many to list."

He might see
improvement by using an intake fan, except that I dont' recall seeing any
slot-mounted intake fans, but if there are any...

There are, or at least used to be, but they don't move much air. I remember one
was 2 40mm fans on a directable 'extension tube'.

Yes, but it goes to the point of stress against the socket, retention
mechanism, or CPU during shipping... just another motivation for Dell to use
this passive 'sink design.

It's just that your assumptions are not necessarily true. Many 'passive'
heatsinks are taller, more metal and longer lever arm, than the 'active'
versions in the design family.

However, being able to deliver the product in an operating condition is a
reasonable design criteria, I would think, as most people don't like loose
broken parts rattling around inside whatever it is they bought.

It doesn't need as much airflow given a 'sink of same efficiency, which is
another issue that could expand this discussion into something more fit for a
book rather than a newsgroup thread. Historically and today, passively cooled
CPUs run hotter,

Than what? You keep trying to compare commercial, toaster oven, systems to what
YOU would put together but the design criteria is not the same. Do some
temperature tests on cookie cutter computers with active heatsinks in them and
you'll find they're just as 'hot' inside.

even though they (all, AFAIK) use a duct.

You make a circular argument. Of course the 'passive' ones will be 'ducted' as
that's WHY they're a passive heatsink in the first place.

To many people
this is considered common knowledge.

It's common knowledge that cookie cutter systems don't have "1C above room
ambient" as the design criteria.

Dumping CPU heat into the case with an
active cooler isn't an issue of the significance that you suggest, since the
airflow is moving in one direction, up and out of the case. Some heated air
is mixed and recirculated though the heatsink but the airflow rate is SO much
greater than even slightly warmer air results in a lower CPU temp.

The localized rate around the CPU socket from case flow is not so great and is
easily overcome by the HSF.

On the contrary, it is optimized to cool the CPU, the exact goal. When a high
quality sink is paired with a low-RPM fan, it is then futher optimized to
have maximum cooling with minimum noise.

If a complete computer system consisted of simply a processor, and nothing else,
then you'd have a point, but it doesn't.

It has widespread adoption because it works well in comparision to the
alternatives of similar cost.

All of a sudden you care about cost.

It works well, yes, but the criteria is as I stated. It 'works' by not making
many assumptions about what the rest of the system will be. That allows
flexibility, and diversification, but at the cost of efficiency.

Yes, the active 'sink works SO well that it can overcome all these obstacles
most of the time.

Of course it does, as long as you don't care about noise, cost, mechanical
reliability, shipping damage, etc.

Not because it's "generic" but becuase it has such a huge
margin over minimal efficiency required,

So does a leaf blower used as a case fan.

that when a decent chassis is used
the active sink works even better, even with a silent fan on it.

As long as you selectively cull the design criteria to fit it.

It's true enough that some people purchase, build, redesign, and outfit their
systems in ignorance, but it has little to do with this topic since these
same folks could either improve or degrade a ducted passive CPU cooling
system using the same methods as on one actively cooled. We both know there
are plenty of crap cases out there too, but that's not an argument towards a
ducted cooling system, but rather to choose the case carefully regardless of
which cooling system will be used.

The same thing goes for comparing a solution based on one set of design criteria
to a different design criteria.

It's usually the situation that user mods to a passively cooled system have a
greater impact, positive or negative, depending on where the fan is located
and whether it's intake or exhaust.

Now this I will agree with, because they are less likely to understand it. I
just wish you'd stop using "passive" in the same context with "fan."

I suppose we just won't come to an agreement... it happens. I do despise long
threads so if you want a thread where we can all argue about passive/ducted
vs active cooling instead of hijacking Peter's thread, that's fine, but I'm
done with this thread.

Ok. My primary objection was the assertion it was a "bad design" and suggesting
'that' is his problem.