Re: AMD's so-called "Cool n' Quiet" feature

Tech-Archive recommends: Repair Windows Errors & Optimize Windows Performance

From: David Maynard (dNOTmayn_at_ev1.net)
Date: 10/03/04 

Date: Sun, 03 Oct 2004 18:42:50 -0500

Chuck wrote:

> I've been down the cooling road several times. The case front air intakes
> are not optimal on most cases, so another source of cool air is needed.

The problem isn't a lack of hole area in the front of the case.

> The
> processor and motherboard chip set need cool incoming air and fans to move
> hot air from the heatsinks. Obviously, the processor is a major source of
> heat.

This is why the rear fan mount is the best (due to the ATX component layout).

> The mbd chipset and any video chipset, card or mbd is the next area of
> concern. Some cases actually need a circulating fan, usually mounted at an
> angle and on or near the bottom of the case. This helps distribute the cool
> air from the front of the case more evenly.

You wouldn't need this if it weren't for the side fan short circuiting the
case cross ventilation draw. Still, it would be best addressed by
increasing the rear exhaust airflow, if possible, rather than an air stirrer.

Unless you have a wall, baffle, shroud, or some other air director, fans
are excellent at sucking their own exhaust right back into their own intake.

> To really tell what air
> direction is best with rear fans and a particular case/power supply, it's
> often necessary to use one of the fan control units that have additional
> thermal sensors that can be placed in areas of concern. (Trial & Error
> testing for the best configuration). The PCI and AGB card areas should be
> measured to make sure that sufficient cooling air is passing thru them.

The best way to deal with an AGP hotspot is a PCI slot fan adjacent to it
or a video card heatsink that exhausts out the adjacent PCI slot: an
'unfortunate' aspect of AGP cards having the main components on the 'wrong
side' with respect to case airflow (one of the things addressed by BTX).

>
> My current temps using a 3g Athalon are
> case 30-34
> hdd 30-32
> cpu 39-42
> video 30-32 (ati 9200) (cheap video card)
> The case uses a side fan with a shroud going to the processor
>
> The general idea is to get the cool incoming air distributed so that hot
> spots are minimized.
> Power supply cooling arrangements vary, and will make a big difference in
> the case airflow and optimum fan usage and airflow direction.

"Optimum" depends on what one wishes to achieve and if noise is of no
concern then placing a half dozen fans all over the place is perfectly
fine, but it's not particularly efficient nor is it quiet.

>
> Last but not least, HDD failure is often due to dry bearings. This may be
> due to higher than desired internal HDD temps.

Generally not a problem if one is active rear exhausting, with sufficient
airflow, and the air intake restricted to coming primarily from the front.
However, I did note that if the front panel air distribution is problematic
then one might want to put a low RPM fan up there for the hard drives,
especially if you have a stack of them (acting as a flow restrictor).

>
> "David Maynard" <dNOTmayn@ev1.net> wrote in message
> news:10m0ilm3f0b972d@corp.supernews.com...
>
>>Opticreep wrote:
>>
>>>Inside my PC is an Athlon 64 3000+ processor, with stock heatsink/fan.
>>> There's also a Radeon 9800 Pro in there. If the computer is idle or
>>>if there's only a light workload (ie internet surfing), the CPU
>>>temperature is around 45 degrees. When there's a heavy workload (ie
>>>games, number crunching, etc), it's often around the late 50s and
>>>sometimes it even reaches the early 60s. Is that temperature range
>>>too hot, or is it normal? Am I better off activating, or
>>>deactivating, the "Cool n' Quiet" feature?
>>>
>>>In addition to the CPU and power supply fan, I have two additional
>>>fans inside the case to circulate air. To get the best air
>>>circulation possible, how should all these fans be arranged?
>>>
>>>Right now, I have the CPU fan blowing air into the CPU's heatsink.
>>>There's another fan on the side panel, blowing air *out* from the
>>>case.
>>
>>Side fans are a bit problematic because they're not really in a good
>>location for cross case ventilation. My first inclination would be
>>exhausting, as you have it, so intake air is pulled from the case front
>>but, depending on how close to the CPU heatsink it is, you might have
>>slightly better luck with it blowing inward.
>>
>>
>>> The third fan is below the power supply, blowing air *into* the
>>>case.
>>
>>That fan should be exhausting outward as, now, you're recirculating warm
>>PSU air going out the rear back into the case with the third fan.
>>
>>
>>> It sounds good on paper, but the temperature inside the case
>>>seems a little high.
>>
>>Basically, you want rear fans exhausting so they remove heat directly and
>>let the airflow come from the front inlets and across the case.
>>
>>Intake fans don't do much other than make more noise, unless you need to
>>specifically direct some airflow at a certain point and can't count on a
>>natural distribution across the inlet venting.
>>
>>Think of the wet noodle analogy. In a typical case, intake fans are like
>>trying to push a wet noodle uphill. Air goes into the case and wafts
>>around just about anywhere, would be nice if it went by the heatsink,
>>going out the first, and whatever, hole(s) it can find.
>>
>>It's much more effective to pull a wet noodle up hill by it's tail. I.E.
>>rear fans exhausting heat directly from the hotspots that are right there
>>and let the cool air come in whatever holes it can find (the front vents).
>>
>
>
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