Scythe NCU-2000 Fanless CPU Cooler

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PERFORMANCE WITH A FAN

There are no mounting points on the NCU-2000 for any fan. This is also true of the NCU-1000. However, mounting a fan directly to this HS is a piece of cake: A bit of wire or string through the fan mounting holes and hooked around the fins would work fine in a tower case. I decided this just had to be tried.


A Nexus 120mm fan covers most of the fins. For the test, it was just placed atop the HS.


SPCR reference Panaflo 80L was also tried.

NCU-2000 Performance w/ Fans (blowing up only)
HS
Idle
Folding
Max Temp
Max Temp Rise
°C/W
TDP
°C/W
MP
No Fan
55
64
72
49
0.71
0.62
Panaflo 80L-7V
43
49
56
33
0.48
0.42
Nexus 120-7V
40
44
49
27
0.39
0.34
Nexus 120-10.5V
39
42
47
23
0.33
0.29
NCU-1000 w/Nexus 120-7V
40
44
50
26
0.38
0.33
* All figures except °C/W in in °C.
TDP (Thermal Design Power of CPU) = 69W
MP (Maximum Power of CPU) = 79W
Ambient temperature = 23°C

It's clear that even a small amount of direct airflow from a fan dramatically improves the cooling performance of the NCU-2000. And the NCU-1000, as well. In fact, a Nexus 120mm fan at 7V (which provides about 20 CFM at a virtually inaudible noise level), virtually erases the performance difference between the older and newer heatsinks. With the Nexus 120mm fan, the cooling performance jumps into higher ranks of Recommended Heatsinks.

MOUNTED IN THE WRONG DIRECTION, WITH FAN

Given the powerful role a fan has on the cooling performance of the NCU-1000, I decided it was time to find out what would happen if the HS was mounted incorrectly (turned 90 degrees so that air flows best through the HS in a horizontal plane) but with a fan blowing towards the rear of the case (if the motherboard was installed in a case).

As I mentioned earlier, screwing the inside bolt under the fins is truly tedious. The photo below explains just why: There's simply no room to move.


Installing the HS with the fins hanging over the bolt means the supplied wrench has to be used.

.
NCU-2000 installed facing the wrong way, with Nexus 120mm fan sucking air through it towards the rear of the case.
The fan was propped on two small boxes placed atop the VGA card; don't try this at home kids!

After this test was run, I kept the HS and fan mounted the same way but put the wood platform back on its feet, thus placing the motherboard on the horizontal plane, as it would be when mounted in a HTPC horizontal case. The results are shown below.

NCU-2000 installed facing wrong way w/ Nexus 120mm fan at 7V
Motherboard orientation
Idle
Folding
Max Temp
Max Temp Rise
°C/W
TDP
°C/W
MP
Vertical
41
45
50
28
0.40
0.35
Horizontal
41
45
49
27
0.39
0.34
HS mounted correctly, motherboard vertical*
40
44
49
27
0.39
0.34
* Data from previous table, with Nexus 120mm fan at 7V
All figures except °C/W in in °C.

TDP (Thermal Design Power of CPU) = 69W
MP (Maximum Power of CPU) = 79W
Ambient temperature = 23°C

As you can see, the performance is virtually unchanged compared to when the HS is mounted facing up/down as recommended -- when there is a fan pushing some air through the fins. In both cases, unrestricted movement of the airflow through the fins and away from the HS is required to achieve this performance.

CONCLUSIONS

The manufacturer's application notes make it abundantly clear that the NCU-2000, when run without any direct cooling fan as intended, should not be used to cool a CPU stress tested with a constant 100% load. Despite this caution, the sample cooled a P4-2.8 adequately to keep the test system from crashing with half an hour of CPUBurn. This was in open air with an ambient temperature of just 23°C. Inside a case with temps at least 10°C higher, the NCU-2000 might not have been able to keep the CPU adequately cool. On the other hand, if the case has one or more fans blowing air near or around the CPU area, it might perform just as well if not better. In the fanless tests I conducted, the NCU-2000 had no help from any sidestream airflow at all; there was no fan producing any kind of airflow that could have helped cooling in any way.

Folding @ Home is a good approximation of the highest loads desktop PC users can expect to reach. With the convection-only test conditions, the NCU-2000 does just barely well enough to keep on the safe side of cool. Again, how well it does inside a real case will depend much on both ambient temperature as well as airflow in the case.

When used exactly as directed -- web surfing, e-mail, word processing, general office apps and playing music or DVDs -- the NCU-2000 will probably do a fine job of keeping a P4-2.8 cool enough in a good but moderate airflow case typical of silent PCs. (Unrestricted case airflow is an important objective for all PC silencers, but those who use the Zen NCU-2000 need to pay particular attention to good case airflow.) Compared to the NCU-1000, the new model is lighter, cools better, and fits both socket 478 and A64 platforms: All of these are positive improvements.

As with the NCU-1000, a 120mm fan power supply makes good sense. Whether the CPU heat passing through the PSU will affect its fan speed will depend on the particular PSU, the heat of your CPU, case cooling and ambient temperature.

With direct forced airflow, there's little doubt that the NCU-2000 can handle >3.0G CPUs. It would no longer be fanless, but that is a somewhat dubious distinction. Given its size and the proximity of the CPU to the PSU fan and/or case exhaust fan, there will almost always be some forced airflow across its fins in any typical system.

The Scythe NCU-2000 Cooler is a significant improvement over the original fanless NCU-1000. It's certainly worth trying for the more sophisticated silent computing enthusiast.

Our thanks to Scythe for the NCU-2000 sample and their kind support.

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