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Scythe Heatlane Zen NCU-1000 fanless CPU cooler

Oct 19, 2003 by Mike Chin

Product Heatlane Zen NCU-1000 CPU Cooler
Manufacturer / Supplier TS Heatronics / Scythe Co., Ltd
Price ~US$60

Heatlane Zen NCU-1000 CPU Cooler is another unusual CPU cooler from Scythe. These are the same people that supplied us with a sample of their unique Kamakaze HSF in the summer. In fact, the Zen is so unusual that the first thing we have to do is show you some pictures:



The base is the same size as the heatsink retention bracket on P4 motherboards.



Looks like the lone skyscraper in an electronic city...

Yup, it is huge. The exact size is W108 x D86 x H143 mm. That's ~4 x 3.5 x 6 inches. Six inches tall. It weighs 615 grams. And it is designed to cool socket 478 CPUs (P4) without a fan. To quote the nicely worded description from Silicon Acoustics, their US retailer,

"The Heatlane Zen NCU-1000 is a true zero dB CPU cooler designed for Pentium 4 Socket 478 CPUs up to 2.8 GHz. The exclusive Heatlane technology is a refinement on the conventional heat pipe which transfers heat through a cycle of vaporization, transportation, and then condensation of a working fluid. The main body of the NCU-1000 is constructed of a very long folded capillary tube, which continually circulates coolant to the furthest fins. The coolant is totally self-contained and maintenance free. There are no moving parts so there is nothing to cause friction or wear. The NCU-1000 is big! It had to be to achieve the surface area necessary to passively cool a modern high performance CPU. The body is an aluminum radiator which interfaces with the CPU through a copper heat spreader."

Yes, it is another heatpipe-derived device. The highly popular article by Fred Mah posted recently was about a fanless homemade heatpipe-based CPU cooling system. The heatpipe in the Heatlane Zen is not obvious; the only sign of this circulating capillary tube, which circulates HFC134 coolant, is right at the top:

Let's go to the description from the manufacturer, TS Heatronics:

"This product is designed with maximum CPU load for P4 up to 2.8GHz as e-mailing, Internet browsing, using word processor, spreadsheet software or equivalent at ambient temperature up to 25C. We assume no liability and provide no warranty for accidents and damages caused by the use of the product at higher CPU load environment than the above. This product does not guarantee performance at high CPU load environment such as data encoding, decoding, benchmark software running, etc."

That's a strong disclaimer, but not unreasonable to state, given that virtually all hardware reviews (including ours) subject heatsinks to the very rigorous test of continuous 100% CPU load, which I've always admitted is the absolute worse case scenario. In real world desktop PC use, few CPUs are subject to that kind of abuse.

Silicon Acoustics adds:

"The NCU-1000 should only be installed in vertically oriented (tower) type system so that convection can be achieved (motherboard up and down, heat sink on its side).

"Recommended configuration: Use the NCU-1000 with a 120 mm fan PSU. The exceptional cooling of the 120 mm fan makes it possible to assemble a virtually silent system with no other cooling fans required. The close proximity of the 120 mm fan intake provides sufficient cooling even under maximum load conditions."

Let's take a step back and show you the box it comes in:

Here are the contents of the box (minus the installation sheet):

Starting with (1) the cooler on the left and going clockwise, there's (2) a bag of bolts, nuts and other hardware, (3) an aluminum plate that is part of the clamping / mounting assembly , (4) a rubber insulator sheet for the back of the motherboard, (5) the retention plate for the back of the motherboard, (6) the copper base of the cooler, and (7) the 1" tall fan decoupling rubber doo-hickey I often use to provide scale perspective in photos. Oh and (8) that little white round thing near the top is a container of thermal goop. Looks like silicone-based thermal interface material.

As you can gather, some assembly is required to go from this collection of parts to the installed cooler setup shown earlier. The manufacturer's website has a detailed PDF manual for download. The assembly is not difficult. Four bolts sandwich the bottom portion of the HS (1) between the copper base (6) and the aluminum plate (3). It ends up looking like this:

The copper plate can be turned 90 degrees from the position shown above. The instructions state that the wider side of the fins structure should face up/down. Which way the copper plate should be mounted depends on the CPU socket configuration of the motherboard. The point is that you want the holes or slots in the heatsink to be facing up/down rather than side/side so that air will flow through them in natural convection.

For the record, the copper base is very smoothly polished. Some fine machining lines are visible but they cannot be felt. Lapping is not recommended.

Installation requires the removal of the standard P4 heatsink retention bracket (made of black plastic). In their place, for sizable bolts are mounted from beneath the motherboard. The aluminum plate (5) goes on the underside of the motherboard, with the rubber insulation piece (4) in between. This naturally requires that the motherboard is removed from the case.



No, it does not rest directly on the motherboard; a rubber pad insulates the plate from the motherboard.



The bolts where the plastic HS retention bracket once was. Ready for HS mounting.

Once the bolts have been secured to the motherboard, the heatsink fits neatly on the motherboard, the bolts lining up to 4 holes on the copper base. Round knurled nuts are used to secure the heatsink. One assumes they are designed specifically to be finger-tightened so that some ham-fisted user with a torque wrench can't abuse the HS or damage the CPU.

NOTE: Tightening these round knurled nuts is a bit fussy, as you have to squeeze your hand and fingers between the PSU and this HS to tighten those knurled nuts. Be patient, go slow. A case with more room between the PSU and the motherboard would be nice, but it seems most have similar spacing, even the tall ones.

TESTING

SPCR's standard heatsink testing method of a Panaflo 80mm low speed fan at 12, 7 and 5 volts. is not applicable here. The design calls for no fan to be used. There's no set way to mount one either, although it is easy to rig up if so desired.

Test platform

Intel P4-2.53 processor. Nominal power is 61.5W; may increase to ~75W if speed throttling doesn't stop it first. 71? C rated maximum junction temp.

Gigabyte GA-81RXP motherboard - Intel 845 chipset; on-die thermal diode monitoring. Modded with large passive heatsink on NB chip for fanless cooling.

Matrox G400 Max VGA card modified with Zalman chipset HS for fanless operation

256 MB DDRAM - PC2100 generic

Hitachi Deskstar 180GXP 30G hard drive (in Smart Drive silencing enclosure)

DigiDoc5 w/ thermal sensors

Antec SLK3700BQE case

Antec SmartPower 350S power supply (Single 80mm fan PSU supplied with SLK3700BQE case)

120mm case fan (1200 RPM max) supplied in SLK3700BQE case

Sunbeam Rheobus fan controller (to control 120mm case fan speed)

Arctic Silver Ceramique Thermal Compound

CPUBurn - Stress program used to load the CPU to 100%. It heats up the CPU a bit more than just about any other utility tried so far.

Motherboard Monitor 5 - Software utility used to monitor temperatures.

TEST RESULTS

1. On the test bench

The system was assembled out in the open with the motherboard flat on the test bench. No fans were anywhere near the CPU heatsink of motherboard. The measurements reflect MBM5's log after ~30 minutes of activity in each category of use.

Open Bench Test
Conditions
Idle
Normal use*
100% CPU load
CPU Temp
38?C
44~58?C
>68?C - freeze
*Normal use much as described by TS Heatronics: web surfing, email, word processing, and playing music or DVDs

The thermal overload under 100% load using CPUBurn occured in little over 10 minutes; the program crashed. As cautioned by the manufacturer, the NCU-1000 is not designed for this kind of stress. However, the straight up vertical position is also not ideal, as indicated by Silicon Acoustics and in the instruction manual provided by the manufacturer.

2. In the case, first try

The system was set up in the Antec SLK3700BQE case with the heatsink fins oriented for best vertical airflow, as per instructions. While the power supply does not employ a 120 mm fan, there is a 120 x 25 mm case fan on the back panel, mounted with soft rubber grommets. It is very quiet but can move a LOT of air; Antec does not specify any details about this fan but they did state that its rated speed at 12V is 1200 RPM. I'd guess the airflow at that speed to be at least 50 CFM, based on specs of other similar fans.

The front hard drive bays were left completely open for maximum airflow. The hard drive in the Smart Drive enclosure was placed on a piece of foam on the bottom of the case. Its noise contribution was negligible.

In-case Test #1
Case fan
CPU Temperature
Idle
Normal use*
100% CPU load
12V
38?C
40~45?C
>67?C - freeze
8V
38?C
41~46?C
>67?C - freeze
5V
44?C
41~48?C
>67?C - freeze

*Normal use much as described by TS Heatronics: web surfing, email, word processing, and playing music or DVDs.

Three things stand out here:

1) In normal use, the temperature is generally lower in the case than it is on the open test bench. This is probably because the 120mm case fan produces more airflow than just convection, and the cooling property of the HS is much better with it horizontal.

2) In normal use, the system is perfectly stable, no crashes or freezes. As noted, the maximum CPU temps vary a bit with case fan speed, but stay under 50C.

3) It still overheats with 100% CPU load -- which is not recommended by the manufacturer.

3. In the case, 2nd try

I decided it was worth trying the cooling mounted the "wrong way" with airflow more optimized to go front-to-back, since the back panel fan was pulling a lot of air through. See the setup below.

In-case Test #2
Case fan
CPU Temperature
Idle
Normal use*
100% CPU load
12V
38?C
39~42?C
>67?C - freeze
8V
38?C
40~44?C
>67?C - freeze
5V
40?C
40~47?C
>67?C - freeze

Temperatures actually improved a bit during normal use but CPUBurn still crashed. It might have taken a few minutes longer for the crash to occur though. So it seems that because of the greater airflow through the back case fan rather than the power supply, this fin orientation provides slightly better cooling.

3. In the case, 3rd try: With 120mm PSU

Well, I didn't give up. Instead, I pressed a Seasonic Super Tornado 300 into service. This is a power supply with a 120mm fan, as recommended by Silicon Acoustics. That fan is capable of blowing something like 70 CFM, but the voltage controller is set up to keep the fan speed very low till above the ~120W DC draw. This system was unlikely to pull that much power, so the PSU fan probably would not spin up much and thus not provide enough airflow for the Zen. We would see.

The Heatlane Zen had to be rotated again. Pull the cooler off, remove the copper base, rotate 90 degrees. Then reattach the base, and install the cooler back on.

Now with those huge 120mm fans at right angles to each other within a couple of inches from the Zen, I began to wonder about turbulence effects. I could picture the air swirling like eddies in a stream, just spinning the heat round and round but going nowhere. Hmm... Banish the image!

Back to the temperature measurements.

In-case Test #3
Case fan
CPU Temperature
Idle
Normal use*
100% CPU load
12V
38?C
39~42?C
>67?C - freeze
8V
38?C
39~43?C
>67?C - freeze
5V
39?C
39~44?C
>67?C - freeze

The normal use temperatures are best with this setup, despite my misgiving about potential nasty interactions between the airflow of the 120mm fans. With the case fan at 5V, this setup is very quiet, measuring just under 25 dBA / 1m (in a 22 dBA room ambient).

CONCLUSIONS

The manufacturer's application notes make it abundantly clear the the Heatlane Zen cooler, when run as intended without any direct cooling fan, is not designed to cool a P4 CPU that is being stress tested with a constant 100% load. This was verified in the testing with many configurations.

When used exactly as directed -- web surfing, email, word processing, and playing music or DVDs -- the Heatlane Zen NC-1000 kept the P4- 2.53 processor well cooled and perfectly stable with virtually any combination of power supply and case fan speed in the test setup. Excellent case airflow should be an objective for all PC silencers, but those who wish to use the Zen (fanless) will want to pay particular attention to good case airflow.

In thinking through about the ideal use for the Zen, I have to admit that Silicon Acoustics' suggestion of a 120mm fan PSU makes sense. But to that recommendation, I would add that it is ideal with a P4 that has relatively lower heat dissipation. In other words, I am not in complete agreement about the "up to P4-2.8" (>68W) recommendation for this cooler. Perhaps if the case cooling provides 50 cfm across the heatsink fins? The P4-2.53 (61W) used in the test may represent something close to the practical high limit of this cooler, if it is run fanless.

If it is provided forced airflow across its fins, I have little doubt that the Zen could easily 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.

One thing I would strongly recommend against is to use this heatsink with a hot P4 in a fanless case. As long as you use it within its limits and intended role, the Zen will be a cool and noiseless addition in your quiet system. Overclockers note: Good case airflow along with, say, 60 CFM directly across these fins, ideally with a 120mm fan, will probably allow you the highest overclock possible with any P4.

All in all, the Scythe / Heatlane Zen NCU-1000 Cooler is a very inventive heatsink for silent operation.

Our thanks to Scythe for the Heatlane Zen NCU-1000 sample and their kind support.

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