You are here

Scythe Kozuti Low Profile CPU Heatsink

Scythe Kozuti Low Profile CPU Heatsink

June 20, 2011 by Lawrence Lee

Product
Scythe Kozuti

CPU Cooler
Manufacturer
Scythe
Street Price
US$30~$35

With the demand for diminutive mini-ITX systems growing in the DIY community, the issue of CPU cooling often comes up. There are a few enthusiast class mini-ITX cases with room for high power graphics cards and bulky CPU heatsinks, but they're pricey and bigger than many may deem necessary. Most mini-ITX cases are sleek and slim, presenting a tricky problem for users, particularly those who prefer whisper quiet machines. Keeping a modern processor cool in a tightly confined space with an adequately low noise level is no small feat.

While some mini-ITX cases can fit fairly capable coolers like the Scythe Shuriken and Big Shuriken, they are far from the norm. Most are slim desktop style models powered using an external power brick and just tall enough just for the board and its I/O panel, with a maximum CPU heatsink height of about 40 mm. Larger variants like the Apex MI-008 are also popular, packing an SFX power supply directly over the top half of the board with around 46 mm of clearance. This is conveniently the same height as the stock heatsinks that ship with the bulk of Intel's current processor lineup (Intel chips are more common for these types of builds due to their superb energy efficiency).



The box.

The Scythe Kozuti is the first candidate we've seen that might have the capability of beating one of these low profile stock coolers while generating better acoustics. The latter shouldn't be hard as stock cooling units are their well-known for being lousy when it comes to noise. The Kozuti is built in the same mold as the Shuriken and Big Shuriken but with smaller dimensions. It features three copper heatpipes, 57 aluminum fins, and stands just 40 mm tall.

The catch? A puny 80 mm fan with an anemic thickness of just 10 mm strategically placed under the fins blowing air directly over the base, rather than through the fins. There is some evidence that this can work as the Noctua NH-C14 performed similarly with one fan whether it was above or below the main fin-stack. The Kozuti will attempt to repeat this result but on a smaller scale.



Package contents.

The Kozuti ships with the necessary mounting hardware, a packet of thermal grease and a simple paper instruction manual. As you can see from the presence of bolts and rubber washers, a hard-mounting system is used for both Intel and AMD installations. Bolts go through the back of the motherboard to secure the heatsink, though no backplate is included as the heatsink's low weigh presents no risk to the PCB.

Scythe Kozuti: Key Features
(from the product
web page
)
Feature & Brief
Our Comment
Super Low Profile CPU Cooler

only 40 mm in height

It's not quite 1U heatsink size (29 mm), but perfect for most low profile cases.
S.F.M.S. (Stealth Fan Mounting Structure)

By introducing the newly developed S.F.M.S. a super mini cooler -no taller than 40mm - is achieved by mounting a fan directly under the fins, which is compatible with more small form factor PCs, such as Mini-ITX case, slim case, etc.
Placing the fan underneath the main fin-stack saves space and allows direct airflow over the CPU socket.

E.I.S. (Easy Installation with Screw)

Easy and safe installation with screws instead of using a backplate.

At 250 grams, the heatsink isn't heavy enough to bend the motherboard PCB so a backplate isn't necessary.

PWM

Fan speed is automatically regulated by the PWM signal of the mainboard. Equipped with new 80 x 10 mm fan, operating within the range of 800 to 3300 rpm, dependent on load.

Standard.
Complies to RoHS standard. That's nice.


Scythe Kozuti: Specifications

(from the product
web page
)
Model Name: Kozuti CPU Cooler
Model No.: SCKZT-1000
Manufacturer: Scythe Co., Ltd. Japan
Compatibility: Intel®:

Socket 775

Socket 1155

Socket 1156

Socket 1366
AMD®:

Socket AM2

Socket AM2+

Socket AM3
Accessory: Installation Guide, Thermal Grease
Heatsink
Overall Dimensions: 110 x 103 x 40 mm /

4.33 x 4.06 x1.58 in
Weight Included Fan: 250 g
Fan
Model Name: PWM 4-pin fan
Model No.: SY8010SL12M-P
Fan Dimensions: 80 x 80 x 10 mm
Fan Speed: 800 (±30%) - 3300rpm (±10%) - regulated by PWM
Air Flow: 6.0CFM ~ 24.82CFM
Noise Level: 8.2 ~ 32.5dBA
Input Power: 2,4 W
Input Current: 0,20 A
Voltage Range: 12 V

PHYSICAL DETAILS

The Scythe Kozuti is composed of a nickel-plated copper base soldered to three copper heatpipes friction-fit to 57 aluminum fins. The cooler measures 110 x 103 x 40 mm (L x W x H) and weighs just 250 grams total.



The Kozuti closely resembles the Big Shuriken only smaller and with the fan placed over the base. This delivers direct airflow over the hottest portion of the heatsink, but makes it more difficult to cool down the bulky fin mass above it.



Due to the curvature of the heatpipes, there is limited space for a fan. The stock unit measures just 80 x 80 x 10 mm with hardly any room to spare.



There is a small gap between the heatsink and the intake side of the fan to reduce turbulence. The wire clips that keep the fan in place are a little loose and vibrate slightly at higher fan speeds. This is unusual as they are typically extremely secure on Scythe coolers.



Despite measuring only 110 mm long and 103 mm wide, it sports a whopping 57 fins in total. On average they are spaced 1.67 mm apart and are just 0.12 mm thick.



Cooling is provided by a nonstandard 10 mm thick PWM fan with sleeve bearings. Typically slim 80 mm fans are 15 mm thick, though they are uncommon and difficult to find.

BASE & INSTALLATION

The most critical aspect of installation is that the heatsink be securely
mounted. A firm mating results in good contact between the heatsink's base and
the CPU heatspreader and more efficient heat conduction. Ideally it should
also be a simple procedure with the user having to handle as few pieces of
hardware as possible.



Like most Scythe heatsinks, the base is nearly perfectly flat and the surface is polished to a mirror finish.



The installation procedure begins with mbounting clips being attached to the base with four tiny screws.



On AMD boards, the backplate and plastic retention bracket must be removed prior to installation. The board is flipped upside down onto the heatsink and bolts with thick padded washers are inserted through the newly vacated mounting holes.



The bolts screw into the mounting clips producing a very secure mating. A similar procedure is used for Intel mainboards.



Fully installed on our Asus 785G test board.

TESTING

Before thermal testing, we took some basic physical measurements.

Approximate Physical Measurements
Weight
210 g

250 g with stock fan and clips
Height 40 mm
Fin count 57
Fin thickness
0.12 mm
Fin spacing
1.67 mm
Vertical Clearance*
39 mm
Horizontal Overhang**
-18 mm
* measured from the motherboard PCB to
the bottom fin of the heatsink.

** measured from the far edge of the heatsink to the top edge of the motherboard
PCB.


Comparison: Approximate Fin Thickness & Spacing
Heatsink
Fin Thickness
Fin Spacing
Phenom II AM2+

stock cooler
0.31 mm
1.03 mm
Phenom II AM3

stock cooler
0.33 mm
1.05 mm
Scythe Big Shuriken
0.33 mm
1.19 mm
Gelid Slim Silence
0.57 mm
1.66 mm
Scythe Kozuti
0.12 mm
1.69 mm
Scythe Samurai ZZ
0.33 mm
1.74 mm
Gelid Silent Spirit
0.36 mm
1.77 mm
Xigmatek HDT-SD964
0.38 mm
1.86 mm
Prolimatech Samuel 17
0.56 mm
1.98 mm
Arctic Cooling Alpine 64
0.87 mm
2.11 mm
Scythe Ninja Mini
0.42 mm
3.46 mm

Testing on larger heatsinks are done on our
i7-1366 heatsink testing platform
, while smaller coolers tackle our AM3 heatsink testing platform. A summary of the test system
and procedure follows.

Key Components in LGA1366 Heatsink Test Platform:

  • Intel Core i7-965 Extreme
    Nehalem core, LGA1366, 3.2GHz, 45nm, 130W TDP.
  • Asus
    P6X58D Premium
    ATX motherboard. X58 chipset.
  • Asus
    EAH3450 Silent
    graphics card.
  • Intel
    X25-M
    80GB 2.5" solid-state drive. Chosen for silence.
  • 3GB QiMonda
    DDR3 memory. 3 x 1GB DDR3-1066 in triple channel.
  • Seasonic X-650 SS-650KM
    650W ATX power supply. This PSU is semi-passively cooled. At the power levels
    of our test platform, its fan does not spin.
  • Arctic Silver
    Lumière
    : Special fast-curing thermal interface material, designed
    specifically for test labs.
  • Noctua 80 mm fan (used when possible with heatsinks that fit 140x25mm
    fans)
  • Nexus 120 mm fan (used when possible with heatsinks that fit 120x25mm
    fans)
  • Nexus 92 mm fan (used when possible with heatsinks that fit 92x25mm
    fans)

Key Components in AM3 Heatsink Test Platform:

  • AMD Athlon II X4 630 AM3,
    2.8GHz, 45nm, 95W TDP.
  • Asus M4A785TD-V EVO ATX motherboard.
    785G chipset.
  • Kingston
    SSDNow V
    30GB 2.5" solid-state drive. Chosen for silence.
  • 2GB
    Corsair Dominator
    DDR3 memory. 2 x 1GB DDR3-1800 in dual channel.
  • FSP Zen 300W
    ATX power supply. Fanless.
  • Arctic Silver
    Lumière
    : Special fast-curing thermal interface material, designed
    specifically for test labs.
  • Noctua 140 mm fan (used when possible with heatsinks that fit 140x25mm
    fans)
  • Nexus 120 mm fan (used when possible with heatsinks that fit 120x25mm
    fans)
  • Nexus 92 mm fan (used when possible with heatsinks that fit 92x25mm
    fans)

The systems are silent under the test conditions, except for the CPU cooling
fan(s).

Normally, our reference fans are used whenever possible, the measured details
of which are shown below.

Reference Noctua 140mm fan

Anechoic chamber measurements
Voltage
Speed
12V
28~29 dBA
1250 RPM
9V
21 dBA
990 RPM
7V
15~16 dBA
770 RPM
6V
13 dBA
660 RPM


Reference Nexus 120mm fan

Anechoic chamber measurements
Voltage
Speed
12V
16 dBA
1100 RPM
9V
13 dBA
890 RPM
7V
12 dBA
720 RPM


Reference Nexus 92 mm fan

Anechoic chamber measurements
Voltage
Speed
12V
16 dBA
1470 RPM
9V
12 dBA
1150 RPM

Measurement and Analysis Tools

  • Extech 380803 AC power analyzer / data logger for measuring AC system
    power.
  • Custom-built, four-channel variable DC power supply, used to regulate
    the fan speed during the test.
  • PC-based spectrum analyzer:
    SpectraPlus with ACO Pacific mic and M-Audio digital
    audio interfaces.
  • Anechoic chamber
    with ambient level of 11 dBA or lower
  • Various other tools for testing fans, as documented in our
    standard fan testing methodology
    .
  • SpeedFan,
    used to monitor the on-chip thermal sensors. The sensors are not calibrated,
    so results are not universally applicable. The hottest core reading is used.
  • Prime95,
    used to stress the LGA1366 CPU heavily, generating more heat than most real applications.
    8 instances are used to ensure that all 4 cores (with Hyper-threading) are
    stressed.
  • CPU Burn,
    used to stress the AM3 CPU heavily, generating more heat than most real applications.
    4 instances are used to ensure that all 4 cores are
    stressed.
  • CPU-Z,
    used to monitor the CPU speed to determine when overheating occurs.
  • Thermometers to measure the air temperature around the test platform
    and near the intake of the heatsink fan.

Noise measurements are made with the fans powered from the lab's variable DC
power supply while the rest of the system was off to ensure that system noise
did not skew the measurements.

Load testing was accomplished using Prime95 or CPUBurn to stress the processor, and the
graph function in SpeedFan was used to ensure that the load temperature is stable
for at least ten minutes. The temperature recorded is the highest single core
reading. The stock fans were tested at various voltages to represent a good
cross-section of airflow and noise performance.

The ambient conditions during testing were 10~11 dBA and 21~23°C.

Stock Fan Measurements

Specifications: Scythe Kozuti Stock Fan
Manufacturer
Power Rating
2.4 W
Model Number
SY8010SL12M-P
Airflow Rating
34.82 CFM
Bearing Type
Sleeve
Speed Rating
3300 RPM ± 10%
Corners
Open
Noise Rating
32.5 dBA
Frame Size
80 x 80 x 10 mm
Header Type
4-pin
Fan Blade Diameter
74 mm
Starting Voltage
6.0 V
Hub Size
29 mm
Weight
40 g
Data in green cells provided by the manufacturer
or observed; data in the blue cells were measured.

The Kozuti's stock fan is an 11-blade sleeve bearing model with open corners and starting voltage of approximately 6V. It has a high nominal speed which is necessary to compensate for its unusually thin form. The proximity of the intake portion of the fan to the heatsink also forces it to spin a bit faster; our sample ran at 3290 RPM on the heatsink and 100 RPM less in open air.

Stock Fan Measurements
Voltage
Speed
12V
3290 RPM
34 dBA
9V
2500 RPM
23~24 dBA
8V
2110 RPM
18 dBA
7.5V
1850 RPM
14~15 dBA
7V
1580 RPM
12 dBA
6.5V
440 RPM
<11 dBA
6.0V
240 RPM
<11 dBA
Measuring mic positioned 1m at diagonal angle from
the center of the heatsink.

Ambient noise level: 10~11 dBA.

The manufacturer's noise rating is very close to what our instruments measured, a very loud 34 dBA at 12V; At full speed it has a high pitched whine which is absent in Scythe's thicker Slip Stream fans. At 9V much of the turbulence disappears, but it's still fairly buzzy. It starts to become quiet at 8V, dropping below 20 [email protected] but retains a bit of a hum all the way down to 7.5V. Like many PWM fans, the speed drops off sharply between lower voltages with a 600 RPM difference between 8V and 7V, and more than a 1300 RPM gap between 7V and 6V.



At 8V, the Kozuti stock fan exhibits tonality at approximately 380 Hz and 690 Hz which manifests in the form of a conspicuous hum.

Cooling Results

Scythe Kozuti
Fan Voltage
Temp
°C Rise
Stock 80mm Fan
12V
34 dBA
46°C
26
9V
23~24 dBA
52°C
32
8V
18 dBA
57°C
37
7.5V
14~15 dBA
60°C
40
7V
12 dBA
65°C
45
Reference 92mm Fan
12V
16 dBA
52°C
32
9V
12 dBA
58°C
38
°C Rise: Temperature rise above ambient (20°C)
at load.

The Kozuti had a wide performance spread with almost 20°C separating its highest speed from its inaudible speed. The performance drop was almost linear with fan speed which is unusual as most small heatsinks typically fall apart when set to very quiet levels. At 7V/12 [email protected], the stock fan kept the CPU's thermal rise above ambient at 45°C; At 55°C our test processor typically begins to throttle down. Our reference 92 mm Nexus fan, simply draped on top of the heatsink, produced a much better result. At the 12 [email protected] level, it kept the CPU temperature lower by 7°C.

Heatsink Comparison Table

°C rise Comparison
20
19
18
17
16
15
14
13
12
Scythe Ninja Mini

(ref. 92mm fan)
-
-
-
-
23
-
-
-
27
Xigmatek HDT-SD964
-
-
-
-
-
22
-
27
34
Prolimatech Samuel 17

(ref. 120mm fan)
-
-
-
-
27
-
-
31
36
Scythe Samurai ZZ
-
-
29
-
-
30
-
-
32
Scythe Big Shuriken
26
-
-
-
30
-
-
37
37
GELID Silent Spirit
25
-
-
-
35
-
43
53
Scythe Kozuti
-
-
37
-
-
40
-
45
AC Alpine 64
-
-
-
34
-
43
-
-
46
Phenom II AM2+
36
-
-
-
-
-
42
-
53
Phenom II AM3
43
-
46
-
53
-
-
-
GELID Slim Silence
-
54
-
-
>60
-
-
-
Gray boxes indicate failure CPU overheating.

We've tested several smallish heatsinks over the past couple of years but the Kozuti proved to be, pound-for-pound, and inch-for-inch, the most efficient model yet. Its thermal performance below 20 [email protected] is outstanding for its size, besting much larger heatsinks like the Arctic Cooling Alpine 64, and two versions of the AMD stock heatpipe cooler. It also gives the Gelid Silent Spirit a run for its money, and actually beats it significantly when their respective fans are dialed down to close to inaudible levels; This is a remarkable accomplishment as the Silent Spirit is three times taller than the Kozuti.

°C rise Comparison (reference fans)
Heatsink
Nexus 92 mm fan voltage / [email protected]
12V
9V
16 dBA
12 dBA
Scythe Ninja Mini
23
27
Xigmatek HDT-SD964
24
30
Scythe Samurai ZZ
25
31
Scythe Big Shuriken

(Nexus 120 mm fan)
24

(12V)
33

(7V)
Prolimatech Samuel 17

(Nexus 120 mm fan)
27

(12V)
36

(7V)
Gelid Silent Spirit
30
36
Scythe Kozuti
32
38

With our 92 mm Nexus reference fan laying on top of the Kozuti, it falls short of Silent Spirit by 2°C. Keep in mind this makes the Kozuti 65 mm tall; if you have that much clearance to work with, the Scythe Shuriken is easily the superior choice.

MP3 SOUND RECORDINGS

These recordings were made with a high
resolution, lab quality, digital recording system
inside SPCR's
own 11 dBA ambient anechoic chamber
, then converted to LAME 128kbps
encoded MP3s. We've listened long and hard to ensure there is no audible degradation
from the original WAV files to these MP3s. They represent a quick snapshot of
what we heard during the review.

These recordings are intended to give you an idea of how the product sounds
in actual use — one meter is a reasonable typical distance between a computer
or computer component and your ear. The recording contains stretches of ambient
noise that you can use to judge the relative loudness of the subject. Be aware
that very quiet subjects may not be audible — if we couldn't hear it from
one meter, chances are we couldn't record it either!

The recording starts with 5~10 second segments of room ambiance, then the fan
at various levels. For the most realistic results, set the volume so that
the starting ambient level is just barely audible, then don't change the volume
setting again.

FINAL THOUGHTS

The Scythe Kozuti is an impressive little heatsink that performs better than we could've imagined. It managed to keep our X4 630 test processor adequately cool even with its fan slowed down to close to an inaudible level. The Kozuti even beat out budget coolers like the Arctic Cooling Alpine 64 and AMD stock heatpipe coolers despite a significant size disadvantage. While the stock fan isn't up to par acoustically with most Scythe models, the end product is as good as it gets for a low profile heatsink. Being just 40 mm tall, it will fit in pretty much any slim case except a 1U chassis and it has more than enough cooling proficiency for a 65W or lower TDP chip.

The Kozuti is currently priced at various e-tailers for US$30~$35. Some
may consider this unfair as the much larger Big Shuriken can be found for approximately
the same amount. The price is not proportional to the amount of materials used,
but it seems somewhat reasonable because it is a rare commodity: A better than
stock cooling solution that can fit in the mini-PC of your dreams.

Our thanks to Scythe
for the Kozuti heatsink sample.




Scythe Kozuti receives the SPCR Recommended Award.

* * *

Articles of Related Interest


Gelid Slim Silence & Prolimatech Samuel 17 Low Profile CPU Coolers
AMD
Phenom II Stock Coolers

Intel LGA1366 Stock Cooler: Good Enough?
Gelid Silent Spirit &
Scythe Samurai ZZ CPU Coolers

SPCR's 2010 CPU Heatsink
Test Platform [Updates: 10 April & 31 May]

* * *

Discuss
this article in the SPCR forums.

Sections: 

Google

www SPCR