Re: 20" iMac G5 overheating?

On 2007-04-21 16:36:40 -0500, The New Guy <replytogroup@xxxxxxxxxxx> said:

If you have hot air exiting, its not being cooled properly.

So where do you propose the heat actually go?

It shouldn't be hot in the first place!

Components like RAM, hard drives, CPUs generate heat. That's a fact of
life. Of *course* the components will get hot in the first place. You
really should think about what you are saying.

Well if we just take the CPU since that generates the most heat: with
a well designed heat sink, it just won't get hot. Its all the
function of the heat sink. If some of you would just read about heat
sinks this would make a little more sense.

No - you are missing basic concepts here. Heat doesn't magically disappear. It must go somewhere, and a well-designed cooling system will move the heat outside of the unit. The greater the difference between the incoming air and the outgoing air, the better job the cooling system is doing.

Regarding ram, you'll
notice that all high end ram now comes with heat sinks. So with a
little bit of airflow the temps are fine. Its all in the heat sink
design.

They have heat sinks because the components get hotter than previous RAM chips did, and air flow over the chip surface, by itself, isn't enough. The heat sinks provide more area for air to come into contact with, allowing for more efficient cooling.

In cooling, first the heat
sink absorbs the initial heat, then air cools the heat sink.

The G5 and Mac Pro CPU heat sinks *do* absorb the heat generated by the
CPUs, and the G5's CPU cooling compartment *does* ensure a steady flow
of cool air enters from the front grill of the computer case, passes
directly over the heat sink absorbing the heat from the heat sink
(thereby cooling the heat sink and equally warming the air), and the
warm air exits promptly out the back grill of the case. The warmer the
air exiting the case, the better job the G5/Pro is doing of cooling the
CPUs.

Did all the G5 towers use water cooling or just some of them?

Only the fastest 2.5GHz model had liquid cooling. All other models had standard air cooling.

A good design would take exterior air to cool the heat generator and
then immediately vent it out.

As hot air, exiting the case? You've said that's not proper.

A properly designed heat sink would not get very hot. The warmed air
would be immediately vented out. (Since its stupid to try to cool
something with hot air.)

You are contradicting yourself. Earlier you said this:

If you have hot air exiting, its not being cooled properly.

Yet now you are seemingly agreeing the air coming out of the back of
the case *should* be hot.
Which is it? (Don't bother answering - those of us who are
knowledgeable about thermodynamics know the hotter the air coming out,
the better job the cooling system is doing.)

To clarify, a good heat sink won't get hot. So the air won't get hot.
But of course it will get warm. And that warmed air needs to be
vented immediately. Hope that makes sense.

The air *is* expelled immediately, due to the design of the case. See:

<http://www.adcom.bg/Web/Apple/Apple_files/designcooling06232003.jpg>

If anyone has found some good interior pictures of the G5 tower,
please post them. Especially with the CPU covers off. I can't
remember what's under them.

Just massive heat sinks:

<http://www.sharpeningbeneath.com/g5guide/>

--
JR

.

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