Re: 20" iMac G5 overheating?

On 2007-04-21 09:37:49 -0500, The New Guy <replytogroup@xxxxxxxxxxx> said:

That just seems like really bad cooling! But cooling was never
Apple's strong point. I wonder if its possible to replace the cpu
heat sink with something better?

Have you seen inside a Powermac G5? All metal fully perforated design,
liquid cooling radiators and fans on both processors ... 9 fans in the
case ... it heats my room quite nicely!

That is exactly what I'm talking about. Very bad cooling design. If
you have hot air exiting, its not being cooled properly.

LOL... You're kidding, right?

The idea of any cooling system is to displace the heat - in other words, move the heat from one undesirable place to another more desirable place. I would say the fact that the G5/Pro displaces as much heat as it does shows that it is in fact doing a *great* job at cooling the components of the G5/Pro. Do you actually propose that heat should stay *inside* the machine? Or are you saying the fact that the components generate heat to begin with somehow equates to bad cooling? : )

The problem
with so many case designs is they try to cool components with warmed
interior case air.

This is precisely what the G5/Pro cooling system does *not* do. It is designed to move cooler air from the outside of the machine (in front of it) through the front vent, across all heat-generating components, and right out the back, and in a very efficient manner. It's pretty much a straight line from front to back. That's why it displaces as much heat as it does.

Which, when you think about it, is rather
difficult. 9 fans....whatever for?

To ensure there is enough constant air flow to displace heat in an efficient manner. Why else?

How many heat generators are
there in that box? CPU (which is liquid cooled in the G5 tower isn't
it?), video card, hard drive(s), and to a very minor extent the ram,
chipset and optical drive (when its working).

You forgot the power supply.

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

Which is exactly what the G5/Pro tower does.

People like the traditional tower computer shape, unfortunately. A
good design would have the hard drives in a separate enclosure to
absorb the high pitched whine they usually generate with a different
type of cooling design than the cpu and video card.

Have you actually looked at the G5/Pro enclosure? The hard drives and CD/DVD drive *are* in a separate enclosure, with separate air flow from the rest of the machine and its own set of fans and heat-sensing hardware so that the OS can independently control fan speed based on heat output. Same goes for the power supply. Same goes for the motherboard.

The cpu fan
produces a lower frequency of noise than the hard drives so the sound
absorption used needs to be different.

Now you are talking about sound absorption, which is an unrelated topic. Break that out into another thread if you wish. I'll ignore it in this instance.

And the power supply should be
external as any power supply using positive cooling can adequately be
cooled with a 120mm fan run on 5 volts, which is inaudible.

Oh that'd be really nice. Yet another box and cord I have to manage in back of my desk? No thanks. Remember: Apple doesn't do crappy design.

The Mac Pro, while still a lousy design for cooling, is much improved.
At least they know better than to use sub 120mm fans. Check out the
hard drive cooling. The first drive gets the fan, and the last drive
cooks.

There are *many* things to consider when designing a case enclosure. Sometimes you have to make sacrifices. People who are good at managing all of the attributes and designing good cases are paid big bucks. If you think you can do better, design a prototype enclosure, make a trip to Cupertino, and present it to Apple. If your designs are good enough, and you show you're not just talking out of your ass and you really do know what you are talking about, I have no doubt in my mind Apple will snatch you up. ; )

I don't know why Apple is so short sighted in the cooling
department. But they've been that way forever. How many hard drives
were cooked in the G5 tower? Squashed up there in the corner.

The fact is the drives get adequate cooling. I have two drives in my G5 tower: a Maxtor 205GB 7200 rpm, and a Seagate 160GB 7200 rpm. I don't allow either one to sleep. The G5 keeps them at a constant 27˚ Celsius. That's just fine.

Has everyone forgot that heat rises?

Not when the heated air is constantly being drawn from front to back in an efficient manner, it doesn't.

--
JR

.

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