CPU Cooler designs?

"Vanguard" wrote in message
...
"Mitch Crane" -three wrote in message
.. .
"Ron Krebs" wrote in
news:GglRg.1011$fl2.452@trnddc02:

I was under the impression that you just want the hot air drawn off
the components. I'm not so sure I'd want cool air pumped over my
CPU.
What happens when a cold front hits a warm front? I'm not
suggesting
it would rain inside my case, but wouldn't condensation come into
play? My box will be in an AC environment and sometimes that cool
air
is actually cold. Now maybe the hot components stay hot enough to
evaporate that, but just to make sure, I'll throw a couple of
silicon
packs in the bottom of my case. Think that'll help? : )

When the cool air hits the warm stuff inside the case it will get
warmer
and the relative humidity of that air will drop. If you had cold
stuff in
the case and you were pumping warm outside air onto it then you
might have
a condensation problem, as can occur with some extreme phase-change
type
coolers.


Guess Ron forgot that the air is *dryer* in winter when the air is
colder hence the higher sales of humidifiers in winter. Silicon packs
are useless when air is moving. They are used in sealed containers to
remove what moisture is there and would be *trapped* there.


I sure did. Problem is, I don't run my box outside in cold, dry winter air.
Nope, it's in an AC environment where they run plenty of humidifiers. And
I'm disappointed my attempt at humor with the silicon packs was taken
literally. I guess I'll have to make a bigger smiley next time. Cheers,

Ron

"Ron Krebs" wrote in message
newsrARg.1486$KK.159@trnddc08...

"Vanguard" wrote in message
...
"Mitch Crane" -three wrote in message
.. .
"Ron Krebs" wrote in
news:GglRg.1011$fl2.452@trnddc02:

I was under the impression that you just want the hot air drawn
off
the components. I'm not so sure I'd want cool air pumped over
my
CPU.
What happens when a cold front hits a warm front? I'm not
suggesting
it would rain inside my case, but wouldn't condensation come
into
play? My box will be in an AC environment and sometimes that
cool
air
is actually cold. Now maybe the hot components stay hot enough
to
evaporate that, but just to make sure, I'll throw a couple of
silicon
packs in the bottom of my case. Think that'll help? : )

When the cool air hits the warm stuff inside the case it will get
warmer
and the relative humidity of that air will drop. If you had cold
stuff in
the case and you were pumping warm outside air onto it then you
might have
a condensation problem, as can occur with some extreme
phase-change
type
coolers.


Guess Ron forgot that the air is *dryer* in winter when the air is
colder hence the higher sales of humidifiers in winter. Silicon
packs
are useless when air is moving. They are used in sealed containers
to
remove what moisture is there and would be *trapped* there.


I sure did. Problem is, I don't run my box outside in cold, dry
winter air.
Nope, it's in an AC environment where they run plenty of
humidifiers.

If it is cooler inside your PC's box than outside, why are you pumping
warm air into it to cause condensation problem?

On Mon, 25 Sep 2006 10:09:06 -0400, wrote:

On Mon, 25 Sep 2006 06:54:20 -0500, "Vanguard"
wrote:



The point is to continually "change the air" inside your case to keep
your components cooler. Whether you have air blowing in (and the air
inside air is forced out) or you have fans blowing out (and outside
air is drawn in) really makes no difference. I have fans blowing in
near the bottom and the fan near the top, including the power supply,
blowing out.

I saw a case mod where the guy had a duct from his AC going directly
into his case and it still wasn't raing or iceing up in there.


The problem is not pumping cold air into a warm case, it
would be pumping warm air into a cold case.

On Mon, 25 Sep 2006 10:09:06 -0400, wrote:

| I saw a case mod where the guy had a duct from his AC going directly
| into his case and it still wasn't raing or iceing up in there.

An AC vent directs cold air toward the front on my computer case where there are
two fans drawing air in. When the AC is on, CPU and mobo temps sometimes report
at less than room temp, especially soon after I turn the system on. Yet, I
never have condensation problems.

Larc



§§§ - Change planet to earth to reply by email - §§§

On Sat, 23 Sep 2006 23:06:52 +0100, Gerry_uk
wrote:

Hi,

As I understand it, most ATX style PC setups have a fan above the CPU
that blows air down onto the CPU to keep it cool, and the hot air
bounces around inside the PC case until it can find an exit (if it's lucky).

As I see it, there are two problems with this,

a) unless you have a vent in the side of the PC case, the air being
taken in by the CPU cooler will not be cool, because it's air from
inside the PC case?

b) the hot air from the bottom of the heat sink ends up warming up the
Motherboard?

I was looking at the Dell CPU coolers of the GX280, GX620 workstaions
(Intel P4 / Pentium D) and the PE2400, PE 2600, PE2800 servers (Intel
Xeon). The design is completely different. The air is sucked in from the
front of the case, straight over the CPU and out of the back - how cool
is that? Pretty cool, and there's hardly any noise either.


So what ??

That's exactly the way it is in conjunction with my rear case fan and
vented front-panel with my Zalman9500 @ 1600RPM on my X2 4400+
( o/c'd to 2.6GHz, absolute max. case temp 48 degrees C). Cools the
memory very effectively as well. The Zalman design is quite brilliant
for its efficiency and smart airflow pattern while still only slightly
over the CPU manufacturer's max. recommended heatsink weight. Which
is no worry on my A8N32-SLI with the provided board-stiffener
in the CPU area.

I am not familiar with the Dell hardware you describe ? BTX-style by
any chance ? In which case a high-performance video card will nicely
bake in the exhaust air from the CPU and memory area. Not surprising
in a totally CPU-centric motherboard design from the same wizards that
brought you the hand and foot-warmer called the P4-Prescott.

John Lewis

--
Gerry_uk

wrote in message
...
On Mon, 25 Sep 2006 06:54:20 -0500, "Vanguard"
wrote:



The point is to continually "change the air" inside your case to
keep
your components cooler. Whether you have air blowing in (and the air
inside air is forced out) or you have fans blowing out (and outside
air is drawn in) really makes no difference. I have fans blowing in
near the bottom and the fan near the top, including the power
supply,
blowing out.

I saw a case mod where the guy had a duct from his AC going directly
into his case and it still wasn't raing or iceing up in there.


Because your friend had the smarts to blow *colder* air into the case
so there would be no condensation when it hit the warmer parts.

Blowing air out the side panel means you are sucking in pre-warmed air
over the CPU before exhausting it. Blowing air into the case directly
at the CPU means you get the greatest temperature differential. Since
the PSU is nearby, the air warmed by the CPU gets drawn out and
exhausted through the PSU rather than over the memory sticks or
chipset. Either just use a hole and shroud with the existing CPU fan
or use a case fan with shroud in place of the CPU fan. Do no have a
case fan next to the CPU fan (but if you feel the need then make damn
sure they blow in the SAME direction and not at or away from each
other). One of the fans will end up restricting the other regarding
maximum airflow. If one blows more CFM than the other then the lesser
CFM fan acts as resistance to the higher CFM fan. This is the same
reason why you need to make sure your case's air intake matches or
exceeds your case's exhaust rate since you can't push out more than
you can suck in (although some have said a slight positive air
pressure inside the case reduces dust accumulation, but I've never
measure the amount of dust collected in my case and simply realize
that I need to blow it out twice a year).

Remember that while a greater temperature differential, using
water-cooled systems, peltier setups, or whatever that you are simply
increasing the possibility of cooling your components as much as
possible. You can't cool them faster than the thermal interface
allows; i.e., you could easily use excessive cooling beyond which the
heat cannot transfer across a metal plate any faster, so the extra
cooling is wasted. Similarly, for air cooling, buying a CPU fan that
is rated 50 CFM won't push that amount of air through the restrictive
air space between the heatsink fins (the fins cause turbulence and the
airflow has to take a 90-degree turn both of which equate to
resistance). You might find a 25 CFM fans cools just as well as a
much noisier 50 CFM fan. In fact, I've seen CPU and case temperatures
drop in some cases by reversing the backpanel fan so it is an intake
fan rather than an exhaust fan (its normal position) but you need to
test in your own case.

On Mon, 25 Sep 2006 22:38:03 -0500, "Vanguard"
wrote:


Blowing air out the side panel means you are sucking in pre-warmed air
over the CPU before exhausting it. Blowing air into the case directly
at the CPU means you get the greatest temperature differential. Since
the PSU is nearby, the air warmed by the CPU gets drawn out and
exhausted through the PSU rather than over the memory sticks or
chipset.

Blowing air in (or having no side fan at all) results in the
most pre-heated air flowing over the memory or chipset.
Granted, the air might be slightly cooler.

The key to reducing warm air flowing in circular or
counterproductive directions is to not interfer with the
time-tested and proven chassis airflow pattern from bottom
front to mid-top rear.

By reducing the bottom front intake rate, by use of a side
intake if not another method, there are lower velocity flow
everywhere except into the 'sink. The exhaust fans will
exhaust at same rate (providing front intake was sufficient)
but a short-loop is created, any air not exhausted into the
air most immedate to the exhaust fan will take a longer path
till exhausted, and slower.

Side intake is mostly Intel's attempt to ship cheaper
heatsinks with P4, particularly Prescott CPUs. A properly
set up system has no need for the side intake and is usually
as well off having it blocked completely. The CPU is not
the only part that needs cooled and the heatsink selected
for it should be selected so as to do the job acceptibly
without other parts running warmer as a result.


Remember that while a greater temperature differential, using
water-cooled systems, peltier setups, or whatever that you are simply
increasing the possibility of cooling your components as much as
possible. You can't cool them faster than the thermal interface
allows;

Untrue/non-applicable. The thermal interface doesn't allow
or disallow, it is only a decrease in efficiency of transfer
from the warmer to the cooler part. This warm vs cool is
the key element as mentioned below.

i.e., you could easily use excessive cooling beyond which the
heat cannot transfer across a metal plate any faster, ...

False. If the cooling isn't much better, the difference may
not be significant change in temp (only a little), and the
CPU may not have needed to run cooler at all, BUT it will
run cooler with a better cooling system and exact same
thermal interface, because the better cooling results in the
cooler of the two parts (warm vs cool), being cooler than it
would have been. Thus, the thermal compound with the same
thermal transfer efficiency, is seeing a higher temp
differential between the two parts which must necessarily
result in a cooler CPU (all else being equal, same thickness
of thermal grease, flatness of mating parts, contact area to
top of CPU, etc).


... so the extra
cooling is wasted.

It might easily be wasted money, time, even materials to
throw away the stock sink (and years(?) later this 2nd sink)
if there wasn't a specific *need* to get the CPU any cooler
(like in an extremely hot environment or high overclocking),
if it ran cool enough to be stable and have acceptible
lifespan, OR if the improvement in the cooling was minimal,
such a slight drop in temp that it varies more by ambient
room temp than anything else.


Similarly, for air cooling, buying a CPU fan that
is rated 50 CFM won't push that amount of air through the restrictive
air space between the heatsink fins (the fins cause turbulence and the
airflow has to take a 90-degree turn both of which equate to
resistance).


A higher free-air rated fan will not push the free-air
volume through a heatsink, that much is true. On the other
hand, given a similar fan (dimensionally matching the other
fan and heatsink and at least as thick) that has the higher
CFM from higher RPM, that will result in more airflow
through the 'sink. Perhaps not a lot more- these fans have
relatively low static pressure potential, but even a little
more, will directly correspond to a reduction in heatsink
temp, which as mentioned above, will ultimately cool the CPU
more.

Increasing airflow has a quickly diminishing return though,
Seldom is it worthwhile to have a fan faster than around
3000 RPM unless a special circumstance or very poor fan
(typically undersized or at least too thin for the
application). Often it is desirable to have even lower RPM,
it can be acceptible to have CPU slightly hotter to
significantly decrease noise if the margin allows for it.


You might find a 25 CFM fans cools just as well as a
much noisier 50 CFM fan.

If all else were equal, no, it is impossible. If the
diameter of fan or thickness, or even an entirely odd
proprietary fan design were used on same heatsink, then
these other factors would have to be considered as well, but
taking same exact fan one can vary the voltage to produce
different RPM - airflow (airflow will increase so long as
the fan isn't terribly undersized and already at it's
practical maximum flow rate into the pressurized area in the
'sink) and see the temp change. It may not change a lot
but it is an inescapable scientific truth that to whatever
extent this air (which is cooler than the 'sink) flow is
increased, there will be a corresponding decrease in 'sink
fin temp, conduction away from the base of the 'sink to this
lower temp region of the fins, and through the thermal
compound to the CPU. The conduction efficiency does not
change with the fixed variables (grease, heatsink metal) but
across mediums (CPU to 'sink or 'sink to air) the higher
temp differential does always result in lower temp.

Naturally if the temp difference is minor, especially if
being reported by a motherboard-mounted sensor, it may be so
slight a change as to be indiscriminable. I am not
suggested anyone improve their cooling at all, unless it is
overheating.

In fact, I've seen CPU and case temperatures
drop in some cases by reversing the backpanel fan so it is an intake
fan rather than an exhaust fan (its normal position) but you need to
test in your own case.

This should never be done, it necessarily increases temps of
other parts (unless the case was otherwise unusual in it's
airflow before this fan was flipped over). Cooling a CPU is
not a game where lowest number wins. Anyone who has a
stable system and CPU that doesn't die prematurely, "wins",
so long as they deem the noise level acceptible. However,
while keeping the CPU cool enough, focus is then shifted to
the rest of the system - a CPU is more heat tolerant than
many parts.

Hi kony,

A properly
set up system has no need for the side intake and is usually
as well off having it blocked completely.

Perhaps, but here's something to try.

Run your ordinary ATX fan cooled PC for two hours in the summer
including some time under load. Measure the CPU and MB temps, then
remove the side panel near the CPU, watch the temps FALL like a brick!

--
Gerry_uk

Blowing air in (or having no side fan at all) results in the
most pre-heated air flowing over the memory or chipset.
Granted, the air might be slightly cooler.

Ah, who needs fans? For peace and quiet you want one of these:

http://home.att.net/~Tom.Horsley/zooty/zooty.html

Proof that you can easily spend as much to get quiet as gamers
spend to get the fastest graphics :-).

"kony" wrote in message
news
On Mon, 25 Sep 2006 22:38:03 -0500, "Vanguard"
wrote:


Blowing air out the side panel means you are sucking in pre-warmed
air
over the CPU before exhausting it. Blowing air into the case
directly
at the CPU means you get the greatest temperature differential.
Since
the PSU is nearby, the air warmed by the CPU gets drawn out and
exhausted through the PSU rather than over the memory sticks or
chipset.

Blowing air in (or having no side fan at all) results in the
most pre-heated air flowing over the memory or chipset.
Granted, the air might be slightly cooler.

Slightly cooler? Try 15 C cooler. While my room temperature is 20 C,
the inside temperature is 35 C (no, I haven't gotten to modding my
home PC's case yet). Actually I prefer a quiet PC so I let Speedfan
slow down the fans which lets the inside get hotter unless
temperatures exceed the configured thresholds whereupon the fans speed
up and are more noisy. Cooler internal temperatures would mean cooler
air over the CPU (and GPU). Having to push warmer air over the CPU
means less efficient cooling. If I can get MORE cooler outside air
inside the case then there would be fewer times when Speedfan would
have to speed up the fans.

The key to reducing warm air flowing in circular or
counterproductive directions is to not interfer with the
time-tested and proven chassis airflow pattern from bottom
front to mid-top rear.

Time-tested? Time has shown that the ATX case was NOT designed for
best cooling. It provides absolutely no zoning of airflow. In fact,
it stupidly enforces turbulence because of the twisting required for
the airflow, and turbulence is resistance to airflow. Do you see any
ATX-style cases that have channels built in to keep flat cables out of
the way so they don't block the airflow? Why did they design it so
hard drives could be shoved against each other (so there is no airflow
between them)? Low front intake is okay for drives in the lower cage
but not in the upper drive cage. ATX (without modification) is a poor
design for cooling.

By reducing the bottom front intake rate, by use of a side
intake if not another method, there are lower velocity flow
everywhere except into the 'sink. The exhaust fans will
exhaust at same rate (providing front intake was sufficient)
but a short-loop is created, any air not exhausted into the
air most immedate to the exhaust fan will take a longer path
till exhausted, and slower.

Short loops are exactly what are needed for zoning the airflows to
minimize them from intermingling with each other. Cool the hot stuff
first with direct outside air and expel it immediately.

Side intake is mostly Intel's attempt to ship cheaper
heatsinks with P4, particularly Prescott CPUs.

Wrong. Side intake was to circumvent the ATX spec's poor airflow
design.

The CPU is not the only part that needs cooled

Exactly, so why use the same airflow to cool EVERYTHING? ATX is a
poor design for cooling. Modders knew that for a long time before
case makers starting adding the extra intake/exhaust ports.

In fact, I've seen CPU and case temperatures
drop in some cases by reversing the backpanel fan so it is an intake
fan rather than an exhaust fan (its normal position) but you need to
test in your own case.

This should never be done, it necessarily increases temps of
other parts (unless the case was otherwise unusual in it's
airflow before this fan was flipped over).

Not if you add MORE venting, like adding a top grill and a bottom fan
that pushes air up past the rear of the drive cages and over the
memory sticks. Top venting may simply be using a PSU that has a
grilled front face instead of just a few slits. I get much better
cooling for *everything* by zoning the airflow inside the case. The
CPU gets cool air from the side panel and its heated air passes out
through the backpanel grill (using shrouds). The daughtercards (i.e.,
video) get their own shroud to pull in air from the side panel intake
and out through a rear grill over the cards (get a fat case to add the
grill or buy one with it already there). Add a grill to the bottom
with a fan to blow up and past the backside of the drive cages and
over the memory sticks (add a top grill if you feel the PSU's fan
isn't adequate or it doesn't have a grilled front face). Keep airflow
as linear as possible and minimize turbulence (which includes changes
in direction).

Many cases don't have fans at the front (unless YOU add them) but
instead just passively suck in the air based on the effective rate of
the exhaust fans. If you now add an intake port midstream in the
case, as in the case of a side panel intake fan, the exhaust fans will
be expelling a portion of that air and drawing less in from the front.
You might end up having to add a fan at the front or around the hard
drives to make sure they get sufficiently cooled, too. If the exhaust
fans were expelling 30 CFM (as their maximum) but a new hole is added
at the side that inputs 10 CFM, the exhaust fans are still only going
to expel 30 CFM so 10 CFM less is coming in from the front to cool the
other parts. So, yeah, I see your point but my point is that the ATX
design sucks for cooling. Better cooling was NOT why the ATX spec was
developed.

Almost everyone has seen that taking off the side panel and simply
pointing a table fan into the case lowers temperatures significantly,
so regardless of the ancient ATX case design, you could use side panel
intake fans to better cool your system provided there was an
equivalent rate of exhaust and you don't mind the noise of the extra
fans.

The ATX design doesn't cool that well so sometimes we have to mod the
case to cool *better*. The old ATX design tried to use one major
airflow pattern to cool off everything. Remember that the first ATX
spec had the PSU blowing air into the case and they later decided it
was better to have the PSU fan suck it out. If you read the ATX 2.1
spec (http://www.formfactors.org/developer/specs/atx2_1.pdf), all it
says about airflow is "Chassis venting should be placed strategically
to allow for
proper cooling of other components such as peripherals and add-in
cards." Oooh, wow, what a scientific airflow design ... not! ATX was
designed for *cheap* integration, not for best cooling. The only part
of the spec that addresses specific airflow is in the placement of the
PSU and its fan in close proximity to the CPU to quickly expel the
heat generated by the CPU so doesn't travel to warm up other
components.

Don't get too hung up on claiming the ATX case was designed for a
particular airflow pattern for best cooling. Its spec was NOT
designed for best cooling and its up to you to mod the case (or get
one) based on YOUR cooling needs and component placement. Obviously
you could mod it wrong but it's pretty easy to mod it right and get
far better results than what the ATX spec was designed for which
itself tells you to mod according to your needs. Designers came up
with BETTER cooling designs while sticking within the ATX footprint,
that's why there are cases with extra intake/exhaust ports (but not
all have them strategically placed). If the ATX design really had
considered cooling, it would've zoned the areas to be cooled where,
for the hottest components, outside air is drawn immediately to a hot
component and expelled immediately without it mingling with any other
airflows. If you're hot and sweaty, do you turn on the fan and stand
on the other side of the room? Do you stand behind some other hot and
sweaty person or go get your own fan? Cooling can be VASTLY improved
over the ancient and inadequate ATX-style case. If you can cut
plexiglass (and heat to bend it, if needed) and glue it together to
make your own shrouds (or find a kit that works for you), along with
nibbling to add fans and intake/exhaust grills, you can zone your own
case and get it running almost as cool (for EVERYTHING) as you could
by simply removing the side panel and pointing a table fan at the
innards.