Cooling experts out there, some help please

[alvin at Mail.Linux-Consulting.com]

hi joel, dan

we use Indek fans...cause its supposedly better in terms
of reliability... we happen to use the noisier ones
cause its cheaper... dont know exact db levels, as its
a moot point,.... noisy fans that are more reliable are
better than cheap fans that is very likely to die ??

measuring temperature with a thermal junction is very 
accurate reading for that junction/area... howerver
when reading the "cpu temperature" over 0.25" die...
the real die temperature will vary widely...

the hot heatsink can distibute the heat evenly across
the die...but....

insidea 1U case...you can only use 40mm tall fans
though some manufacturers use a 60mm fan that is tilted at
45degrees... the blades in a 60mm fan can push more air...

we replaced the 1.5" or 2" tall intel p3 heatsinks with
a 0.25" (total height) heatsink/fan combo that works really well
in our 1U case.... we've not attempted similar issues for
AMD cpus, as there is no "metal clip" that works for
the any heatsink/fan that will fit inside the 1U...
that allows for 0.5" - 1" of air space above the fans

we have 3 cpu side fans that blows air across the cpu heatsink
in addition to the normal 0.25" heatsink/fan that sits
ontop of the cpu/die
	- if one fan dies... we should still be okay...

have fun
alvin
http://www.Linux-1U.net ... just gotta keep the air flowing..out...


On Mon, 21 May 2001, Joel Jaeggli wrote:

> http://www.netroedge.com/~lm78/cvs/browse.cgi/lm_sensors2/doc/FAQ
> 
> > I just tried lm-sensors/i2c on a dual processor PIII system and it
> > reports that the cpu temps are +2C when idle and around 16C when
> > loaded.  Obviously these are wrong.  The question is, are they
> > usually wrong by a constant amount?  So can I assume that my
> > cpu's are at something like 32C when idle and 48C when loaded?
> 
> it's likely that the value is offset. I'd take a look at the value in the
> bios and figure out what the offset between that value and the idle value
> is.
> 
> > I want to know this because I want to disconnect some of the eight
> > fans that the retailer put into this box!  Seems a bit excessive
> > to me (and noisy) but I don't want to mess with it without knowing
> > for sure whether they are needed.
> 
> I typically measure that sort of thing with a thermal probe and a
> multimeter. casue the mainboards sensors may not be in useful locations
> for extremely accurate measurements.
> 
> boxs are typically designed with their worst case rated operating
> temperatures as the target for the volume of air they have to move... in
> racks in a datacenter, particularly in the event of hvac failure operating
> margins afforded but exhausting more air are desirable.
> 
> > Anyone have any good recommendations for quiet fans?  Or fans
> > that only switch on when things get hot?
> 
> panaflo FBA-08A12L. 80mm x 25mm is a pretty quiet (21dba at 1900rpm) 80mm
> fan, but it's fairly low volume for a 80mm fan, 24cfm, compared to say a
> delta 4300rpm 80mm fan (pretty standard pc fan) which is 48.5dba (more
> than 2 orders of magnitude louder) at 68cfm...
> 
> Thermally controlled fans are pretty common, but in pc's having the
> thermostat on the fan isn't enough, it needs to be on or near the
> components you're trying to cools. vendors do make i2c controllers that do
> this, but it's a lot of work as a retrofit.
> 
> > Dan
> >
> >
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> 
> -- 
> --------------------------------------------------------------------------
> Joel Jaeggli				       joelja at darkwing.uoregon.edu
> Academic User Services			     consult at gladstone.uoregon.edu
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> --------------------------------------------------------------------------
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> the right, 1843.
> 
> 
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