Shortest Passive CPU Cooler?

Borris

Borris

Borris

Caporegime
Joined
25 Oct 2002
Posts
30,409
I need a cooler that has a low profile - my case is 5.25", and there is a full-size DVD-R squeezed in there too (so the effective clearance is more like 3", including MoBo & CPU).

It needs to be Socket 478, but doesn't need to be particularly efficient as I'll be running an undervolted P4 M, and I'll be happy with passive - which it would probably have to be anyway, otherwise the airflow would be all out of whack.
 
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Why is aluminium better for passive?

Copper heatsinks offer superior cooling for all situations don't they?

The only downside to copper is cost, weight and more difficult to machine.
 
***F1ZZY*** said:
Why is aluminium better for passive?

Copper heatsinks offer superior cooling for all situations don't they?

The only downside to copper is cost, weight and more difficult to machine.
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Copper is more dense and therefore holds the heat longer as well and being more efficient at conducting it, when you don't have a fan to aid the removal it quickly builds up.
 
Raikiri said:
Copper is more dense and therefore holds the heat longer as well and being more efficient at conducting it, when you don't have a fan to aid the removal it quickly builds up.
Click to expand...

This was pretty much what I had heard, in a passive situation aluminium fins seem to have an advantage over copper for heat transfer, though I think a copper core is still advantageous.
 
Raikiri said:
Copper is more dense and therefore holds the heat longer as well and being more efficient at conducting it, when you don't have a fan to aid the removal it quickly builds up.
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eh??

Copper is more dense so can hold more heat (assuming same size HS)

It is better at conducting..TRUE.

Surely getting hot and removing more energy away from CPU is better.

We're not starting this "aluminium dissipates heat faster" stuff again are we?

I fail to see how passive aluminium is better - assuming same size HS, and in the OP case he wanted a small, low profile one. Surely it better to have that small space filled with as much copper with the largest surface area as possible.
 
***F1ZZY*** said:
eh??

Copper is more dense so can hold more heat (assuming same size HS)

It is better at conducting..TRUE.

Surely getting hot and removing more energy away from CPU is better.

We're not starting this "aluminium dissipates heat faster" stuff again are we?

I fail to see how passive aluminium is better - assuming same size HS, and in the OP case he wanted a small, low profile one. Surely it better to have that small space filled with as much copper with the largest surface area as possible.
Click to expand...

Well to be honest I've not seen anything to justify using either, I've never tried it myself.
 
And eventually the copper will reach it's limit as it is unable to dissipate the heat, that means it's efficiency will drop and the CPU will get hot, quickly.
 
Raikiri said:
And eventually the copper will reach it's limit as it is unable to dissipate the heat, that means it's efficiency will drop and the CPU will get hot, quickly.
Click to expand...

Eh????

What limit??

Excuse the following approximations-IIRC

Copper is ~ 3 x density of aluminium
Aluminium has ~ twice the specific heat capacity

= same size HS holds more energy if made from copper. ~1.5 times the energy.

The biggest advantage of copper though is it has roughly 3 times the thermal conductivity.

So it can absorb more heat and spread it faster throughout the HS.

The only real world advantage for aluminium is it is less dense so we can have a much bigger HS (surface area is where we get good performance as the limiting factor is the poor thermal conductivity of air).

As space is limited for this guy, he will be better off with copper.

If space is not limited then we want big, large surface area and here aluminium wins due the the density/weight. We don't want copper coolers the size of the ninja or XP-120 or they would rip the sockets off mobos; but for sure they would cool better :D
 
Borris, sorry for going off topic :p

Your clearance is 3 inch, that is actually quite large. Without knowing your proper dimensions it is hard to advise.

3inch ~ 75mm (how much taken up by mobo, socket and chip??)

Lets assume you have a physical 65mm of clearance. That is actually not that small..!! :eek:

An xp-120 is only 63mm, would it fit (only you can decide this) I know it contradicts my previous theories on Al vs Cu but the xp-120 is soooo damn huge, if it will fit then it will be cool (pun intended).

You could also try the SP-94 (another thermalright offering) as its pure copper and only 45mm tall.

Note - none of these heatsink are designed for passive, their fins are way too close together.

Final consideration from me, is to look at the zalman CNPS7000B-Cu. It is 62mm tall but has a fan built in (recessed). The fins are more spread out so might be ok passive, but you can always have the fan come on, at maybe 50% speed, if temps get too high.

I'm pretty sure all would do justice on an undervolted P4M. (probably even overkill - he he what's that!!!)

Good luck :D :D :D
 
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I went for the AK-360 in the end, but changed the slimline stock fan for a 60mm acousitfan.

After lapping the bejesus out of it, I then indulged myself in some very technical and precise mechanics, in order to fit the new fan into the bracket.

Pliers and a hammer are technical, aren't they?

Airflow is still a problem though - the case chassis itself is hot to the touch (although it is a heatsink case), but the PSU is blowing cold air out - I may just flip the fan to pull air in.

Thanks for the pointers though.
 
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