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Using a 80mm Fan on 60mm Heat Sink

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SamDaMan

Registered
Joined
May 27, 2001
I been using a coolmaster 6I11 on my 1.33 G Athlon. Its noisy as can be. I have some Papst 80MM fans in the case. I have a ton of space. I thinking to mount the quiet 80MM fans on the coolmaster heatsink which seems nice and big and thick. I found this artical and a couple of links. Does anyone have any ideas on this (i.e. is it effective) or more links to others who have tried it?

From someone else:

Given:
1. An Intel FC-PGA on a slotket.
2. Clearance in the case & motherboard

Goal:
1. Allow the maximum in air cooling for overclocking without raising the noise level.

Assumptions made:
1. The Intel version of the Alpha PEP66 is the same as the AMD version of the Alpha PEP66 reviewed here.
2. C/W does not change if the Watts output by a CPU decreases.

Then:

An Alpha PEP66 with a 27 CFM fan has a C/W of 0.23. An Intel 550E MHz radiates 14.5W = ~3.3 deg C over ambiant.
An Alpha PEP66 with a 27 CFM fan has a C/W of 0.23. An Intel 1.13 GHz radiates 35W = ~8 deg C over ambiant.
An Alpha PEP66 with a 33 CFM fan has a C/W of 0.19. An Intel 550E MHz radiates 14.5W = ~3 deg C over ambiant.
An Alpha PEP66 with a 33 CFM fan has a C/W of 0.19. An Intel 1.13 GHz radiates 35W = ~7 deg C over ambiant.

Yes, I know that the Intel 1.13 GHz is nonexistent. I am using it as a worst case.

It is intersting to note that the temperature drop is at most 1 deg C. This is not too surprising given that the test setup for the reviews used a processor generating a heat load of 69.2 Watts. The difference between the 27 CFM and the 33CFM fans was 2.6 deg C. Half of the heat load is approximately equal to a 1.13 Ghz; half of the temperature delta is 1.3 deg C. This is close to the 1 deg C calculated above. So the math checks out.

Now a Papst 8412NGML 80mm fan is rated at 21.0 dBA and 26.5 CFM. That is approximately equal to the 27 CFM flow used above. The noise level is less than that of a whiser (23 dBA). The only problem is that this is an 80mm fan, and the PEP66 uses 60mm fans. No matter. All I have to do is buy/make a converter from 80mm to 60mm.

Now a Papst 8412NGM 80mm fan is rated at 26.0 dBA and 34.1 CFM. That is approximately equal to the 33 CFM flow used above. The noise level is louder than that of a whiser (23 dBA) and is the same as that of a Golden Orb. Again, the only problem is that this is an 80mm fan, and the PEP66 uses 60mm fans. No matter. All I have to do is buy/make a converter from 80mm to 60mm.

This should allow me the maximum in air cooling for overclocking without raising the noise level. Depending on which fan I get, I will also replace the 80mm fan in the power supply with the same fan so that the gains made in using the heatsink are not washed out by a noisy power supply.

Questions:
1. Does C/W change if the Watts output by a CPU decreases? I do not think so.
2. Anyone see a problem with anything?


Some links on this subject:


 

batboy

Senior Moment
Joined
Jan 12, 2001
Location
Kansas, USA
Wow, you've been doing a lot of thinking and research on the subject. Yes, exchanging the 60mm CPU cooler fan for an 80mm fan is a great idea. I did the same thing to my FOP cooler. Using a PEP and a slotket, you might block one of your RAM slots.

Another idea is to replace the power supply fan with a thermister controlled fan like I have in my Antec power supply. This speeds up the fan as it gets hot and slows it down as it cools. Higher fan speeds (rpm) equals more noise. Thermister fans are not that much more expensive than regular fans.
 
OP
S

SamDaMan

Registered
Joined
May 27, 2001
I done even more research:

This seems the best heatsink:


Here is the 80mm - 60mm converter (its there somewhere I can't link to exact page "DownBurst") it is all aluminum for even more heat dissipation.


Here is the best / quietest 80mm Fan: (Its pabst) 8412 NGL not the right power connecter, I'll see if they have one that attach to mother board 3 pins instead of the 4 pins powersupply. 1600 rpm for 28 cfm. Should be quiet. And as suggested above you use the 8412 for the power supply and for the case fans so they is all the same noise level.



There it is I gonna put all this together and that should be the end of it.
 

batboy

Senior Moment
Joined
Jan 12, 2001
Location
Kansas, USA
That 80mm fan with the 28 CFM flow should be very quiet, but it don't flow very much air. If you're thinking about doing much overclocking, you may wish to consider something with a little higher CFM. If quietness is more important than overclocking, then go for what you have picked out.
 

sifu quoc

Member
Joined
Dec 17, 2000
i found that higher cfm from a 80mm fan didnt do much vs my 60mm delta....

it was a lil bit quiter than the delta, but performed like my delta at 7volts....

i made my own 80 to 60 adapter... now my delta is back on....