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overcoat

Active CPU cooling for the Gen8

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overcoat

As I was going to be swapping out the motherboard and fan on my unit, while it's apart I thought I'd take the opportunity to look at other cooling options for the CPU.

 

This might be of interest to those who've fitted a 69W Xeon. You can see psikey's stress test of a 45W Xeon and the OE passive heatsink here, it stays quite cool.

 

There are two challenges fitting a CPU cooler to the Gen8; the minimal height available and non-standard cooler mounting holes.

 

Unfortunately rather than the standard 75x75mm mounting holes for a LGA1155, this motherboard has 75x65mm. That means the diagonal distance between the screws changes from 106.07mm to 99.25mm.

 

The solution I found was the Akasa K25. Due to the 10mm change in mounting dimensions, only one diagonal pair of mounts was going to line up.

 

gallery_5001_64_9191.jpg

 

 

The mount on the right side above needs to be bent up to clear that corner of the metal CPU retainer. If I'd had access to my Dremel I'd have nipped the two unused mounts off.

 

gallery_5001_64_53478.jpg

 

 

A side view of the fitted cooler showing good contact. I reused the screws and springs from the passive cooler and added 6 washers to increase the tension.

 

gallery_5001_64_74035.jpg

 

 

When fitted there is heaps of clearance.

 

gallery_5001_64_48160.jpg

 

 

This last photo shows the TIM was very evenly spread between the CPU and cooler.

 

gallery_5001_64_2381.jpg

 

 

Even though the cooler is only attached by one pair of screws, it does not rock in the slightest. The K25 is quite light and as the motherboard is horizontal I'm not worried about it at all.

 

The TIM is Arctic Silver Céramique 2 which is also very sticky once it has been heat cycled.

 

Of particular interest to me, the K25 is completely silent in use :)

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Joe_Miner

Wow! +1!  Fantastic Posting OverCoat (absolutely love the pictures too)!

 

Thanks!!

Edited by Joe_Miner

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gstarks

Would be interesting to see some steady state temp readings from iLO (case closed, idle/busy for extended period), comparing this to the passive heat sink for the same CPU. 

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overcoat

I currently have the original Celeron in to repro for my SATA AHCI support case and capture Active Health System logs.

 

As the case fan runs at a minimum of 36% like this, at the moment I can't do a meaningful stress test to compare results.

 

With the passive heatsink the Celeron idles at 40C. With 100% load on both cores it stayed constant at 40C due to the case fan speed...it was under load for 100 minutes.

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ikon

Nice work overcoat. Never would have thought you could find a CPU cooler that would fit in such a tight space. I'm very interested (like gstarks) in see what kind of temps you get. And the photos are stellar -- such nice, clear macro work.

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gstarks

I currently have the original Celeron in to repro for my SATA AHCI support case and capture Active Health System logs.

 

As the case fan runs at a minimum of 36% like this, at the moment I can't do a meaningful stress test to compare results.

 

With the passive heatsink the Celeron idles at 40C. With 100% load on both cores it stayed constant at 40C due to the case fan speed...it was under load for 100 minutes.

 

Definitely focus on the repro for the fan speed issue as that is far reaching.  thanks for your help on that!

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overcoat

I certainly will! FYI the replacement hardware didn't change its behaviour, as I expected ;)

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Cadd70

How did you get power to the cpu fan ?

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overcoat

I converted the 6 pin fan connector to the conventional 4 pin PWM connectors you get on consumer gear, the Delta case fan now has a female PWM connector where I cut the wires.

 

In the photo below you can see only the RPM and PWM wires are connected to the mobo. I also left the two connected ground pins intact so it still 'knows' the fan connector is fitted.

 

I've taken +12V and ground from the SATA wiring harness for the drive bay, negating any risk of drawing excessive current through the mobo.

 

That first PWM connector is joined to an off the shelf Y adaptor.

 

The side of the adaptor with all 4 wires goes to the case fan so everything appears stock (i.e. its reported RPM) to the Active Health System.

 

The side of the adaptor with only 3 wires, excluding RPM, goes to the CPU fan.

 

As the PWM wire is connected this fan can share the control signal with the case fan, thus it speeds up and slows down in harmony with the case fan :)

 

 

gallery_5001_64_32484.jpg

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overcoat

As it looks like there's a firmware fix coming for the AHCI fan speed issue, I put my Xeon back in and got some temps with the CPU cooler.

 

gallery_5001_64_195.png

 

gallery_5001_64_29755.png

 

It works a lot better than I was expecting but I'll run the test again once the case fan has been slowed down.

 

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