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Cooling with Alpha PEP66

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lifeguard1999

New Member
Joined
Dec 18, 2000
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?