Scythe Mugen 5 Rev. B Heatsink Review

Scythe has long been an everyday name in the PC cooling market with their various heatsinks and fans throughout the years. Today, we have a revised version of Scythe’s Mugen 5 CPU heatsink sporting compatibility with most current CPU sockets from Intel and AMD. The Mugen 5 is a typical single-tower style heatsink with one fin stack, as opposed to their dual tower FUMA heatsink or much more massive Ninja 5 heatsink.

Specifications & Features

(Courtesy of Scythe)

Scythe Mugen 5 Rev. B Specifications
Model #SCMG-5100
Dimensions130 x 154.5 x 110 mm (including fan)
Weight890 g (including fan)
Socket CompatibilityIntel: LGA 775/115x/1366/2011/2011-v3/2066
AMD*: FM1/FM2(+)/AM2(+)/AM3(+)/AM4
Baseplate/Heatpipe MaterialNickel-plated copper
Fin MaterialAluminum
Heatpipes6 x 6 mm
Fan Specifications
ModelKaze Flex 120 PWM
Model #SU1225FD12M-CHP
Fan Dimensions120 x 120 x 27 mm
Fan Speed~300-1200 RPM (PWM controlled)
Noise Level~4-24.9 dBA
Air Flow~16.6-51.17 CFM / ~28.2-86.93 m3/h
Static Pressure~0.75-10.3 Pa / ~0.076-1.05 mmH2O
Bearing TypeSealed Precision FDB
Input Power1.56 W
Voltage12 V
Amperage0.13 A

* Please note that an original backplate with screw mounting is needed for installation on motherboards with AMD sockets. Please check before buying if the backplate is fixed by screws or plastic pins! If the backplate uses plastic pins, mounting this cooler is not possible.


Asymmetric Design

Ram modules with large passive heat sinks are no problem for the Mugen 5 Rev. B. Its heat pipes are gently sloped backward so that the radiator is not centered directly above the baseplate, but slightly offset. This asymmetric design allows unrestricted access to the memory banks.

Kaze Flex 120 PWM Fan

The Mugen 5 Rev. B is equipped with a PWM fan with a control range of 300 to 1,200 RPM from the newly developed Kaze Flex series to ensure a high level of stability and an average lifespan of 120,000 hours. The self-contained liquid bearing (Sealed Precision FDB) reduces friction and wear to a minimum with the help of a special oil film. Rubberized pads have a decoupling effect and prevent the transmission of any vibrations.

H.P.M.S. II (Hyper Precision Mounting System II)

The updated Hyper Precision Mounting System II now features full compatibility to AMD®s new AM4 platform. A preassembled mounting bar simplifies the installation process, while spring-loaded screws prevent uneven pressure distribution. The Mugen 5 Rev. B package also includes an extra-long screwdriver for easy mounting.

Dual Fan Mount Structure

Like its predecessors, the Mugen 5 Rev. B was designed to mount a second fan (not included). This leads to increased cooling performance by making use of the push / pull principle. A second set of fan-clips is included.

Packaging & Accessories

Scythe’s packaging is always full of information for potential buyers giving them everything they need to know to determine if the heatsink is the right buy. On that front, there is an excellent isometric picture of the Mugen 5 with the Kaze Flex installed. Of course, Scythe’s logo is in the top right and compatibility is listed here as well. On one side, we have detailed specifications and dimensions for the heatsink and fan. The other side highlights four features, including the asymmetrical design, Kaze Flex fan, H.P.M.S. II mounting system, and the ability to mount two fans.





Opening the box reveals the partially foam-wrapped Mugen 5, the Kaze Flex 120 fan, and the box of accessories.

Box Contents

The accessory box includes an installation manual, hardware bag, and a long screwdriver. The screwdriver is a nice touch, as I’m sure anyone can appreciate not having to find one off-hand or even buy one just to install the heatsink. The bag has a tube of thermal paste, backplate, Intel/AMD brackets, press-fit spacers, screws, and two sets of fan clips for those wanting to install an additional fan.

Accessory Box Contents

Hardware Bag Contents

The fan included with the Mugen 5 is a PWM version of the Kaze Flex 120. This fan runs up to 1,200 RPM and consumes 1.56 W of power. As far as looks go, it has a black frame with gray blades which will blend in with the majority of builds. The gray corners on the fan are rubber which to minimizes or even eliminates any vibrations that could occur while the fan is in operation.

Kaze Flex 120

Kaze Flex 120

Scythe Mugen 5 Rev. B

The Mugen 5 s made from aluminum and nickel-plated copper which gives it a uniform metallic finish. here are six heat pipes forming a u-shape through the base with the ends capped off on top of the heatsink. The fin stack has 39 fins with a density of around 10 fins per inch, so there’s plenty of room for airflow across the heatsink. We can also make out some of the asymmetrical design and notched bottom edge, but we’ll get a good side shot in a bit.

Scythe Mugen 5 Rev. B

Scythe Mugen 5 Rev. B

Scythe Mugen 5 Rev. B

Scythe Mugen 5 Rev. B

Here are the same isometric shots, but with the Kaze Flex 120 installed. We can see the fan clips are attached to the fan’s outermost mounting holes, which means only 25 mm thick fans can be used with these clips. However, clips that attach to the innermost fan mounting holes would allow for fans of any thickness, providing nice flexibility in fan use.

Scythe Mugen 5 Rev. B

Scythe Mugen 5 Rev. B

Scythe Mugen 5 Rev. B

Scythe Mugen 5 Rev. B

With a true side view of the Mugen 5, the asymmetrical design can be seen in more detail. The heat pipes bend towards one side placing the fin stack off-center of the base. This, along with the notched bottom edge, allows for better memory compatibility and easier access to the DIMMs.

On the top, we have the 12 heat pipe end caps, two holes, and the Scythe logo. The two holes in the top of the heatsink allow the included screwdriver access to a couple of the screws on the mounting crossbar.

Side View – Asymmetric

Top View – Screwdriver Holes

The base is nickel-plated copper just as the heat pipes, and is very close to a mirror finish.



Now, we’ll go through a mock installation to show all the steps involved when mounting the Mugen 5. The first step is to mount the backplate onto the motherboard with four thumbscrews. You’ll need access to both sides of the motherboard simultaneously to hold the backplate in place while securing the thumbscrews. They can then be tightened down with the included screwdriver.


Backplate Mounting Screws

Once the backplate has been installed, the cross braces are secured with four screws and the included screwdriver.

Mounting Braces

Mounting Braces Installed

The next step is to apply thermal paste to the CPU, and Scythe kindly includes a tube of paste for those who may not have any. I personally use the “dot” method of applying thermal paste by using a blob of paste the size of a small pea or so in the center of the CPU and let the pressure of the heatsink spread the paste across the CPU. Once the paste is applied, we can mount the Mugen 5 by using the screwdriver and alternating between screws every few turns to apply pressure as evenly as possible until the heatsink is securely mounted.

Crossbar Screw

Crossbar Screw

The final step is to install the Kaze Flex 120 on whichever side of the heatsink you prefer and is best for your system. Remember, Scythe included a second set of fan clips to install fans on both sides of the Mugen 5 for a push/pull configuration if so desired.

Fan Mounting

Test Setup & Methodology

Test Setup
CPUIntel i7 8700K @ 4.7 GHz, 1.125+ V
MotherboardASUS ROG Strix Z370-F Gaming
RAM2 x 8 GB G.Skill TridentZ DDR4-3200 15-15-15-35
StorageIntel SSD 660p Series 1 TB M.2 NVMe
PSUSeasonic X-750 Gold
HeatsinksAlphacool Eisbaer Extreme 280 (Stock)
Enermax Aquafusion 240 (Stock)
Scythe Fuma Rev. B (Stock)
EVGA CLC 240 (Stock)
Noctua NH-D14 (Stock)
be quiet! Dark Rock 3 (Stock)
Thermalright Venomous X (1x Gentle Typhoon AP-15 w/ 25 mm shroud)
Fluke 52 II Dual Input Thermometer
Tenma Sound Level Meter


All testing was performed on an open test bench, which minimizes ambient temperature and gives a “worst case” scenario for sound level.

Cooling performance was tested as follows:

  • Disabled all BIOS settings that cause the CPU clock speed and/or Vcore to fluctuate (although there was still some Vcore fluctuation under load).
  • Ambient temperature was measured with a Fluke 52 II at ~1 inch from the intake fan(s). Then, subtracted from the recorded temperatures to get ΔT.
  • Varied Vcore (in BIOS) from 1.125 V to 1.375 V in 0.050 V increments to increase heat. Stopped increasing Vcore once a core reached ~100 °C.
  • 20-pass 2048 MB RAM LinX runs at each Vcore interval were used to load the CPU.
  • CoreTemp was used to record minimum and maximum core temperatures.

Sound level in dBA was measured 10 cm from the intake fan with the fan speed set to 100%. Then, the sound level was estimated for other distances using the following formula:

L2 = L1 – 20 * log10(r2/r1)

  • L2 = dBA @ desired distance
  • L1 = dBA @ reference distance
  • r1 = reference distance
  • r2 = desired distance

Why estimate sound level instead of measuring at further distances? It’s because the meter I’m using is most accurate between 40-130 dBA, so I needed to measure really close to the source to make sure my readings were within that range to get the most accurate measurements.


Cooling Performance

Performance lands in the expected range with the other two single-tower heatsinks, a Dark Rock 3 and Venomous X. Looking at the middle-of-the-road Vcore (1.225 V), all three single-tower heatsinks have virtually identical performance. The dual-tower coolers, FUMA and NH-D14, have some separation; followed by the liquid coolers forming even more separation from the pack.

When looking at the high Vcore range all of the air coolers’ performance plots are more grouped, and the liquid coolers retain their performance keeping their plots separated from the rest.


Sound Level

The Mugen 5 has a very good showing in the noise department due to the 1,200 RPM Kaze Flex fan(s). The only heatsink with lower noise in my testbed is the Venomous X paired with a 1,850 RPM Scythe Gentle Typhoon fan (with 25 mm shroud). So, there’s definitely headroom to add beefier fans for better performance while still keeping the noise level low. So, the three plots with the lowest SPL all include Scythe products.


Scythe’s Mugen 5 Rev. B is a good looking cooler with a bare metal aesthetic that goes well with any theme. Capped heat pipes and a subtle Scythe logo on the top fin cleans it up nicely.

A few details about the Mugen 5 that I can appreciate is (1) the asymmetrical design along with a notches bottom edge to allow for great RAM support and access, (2) the included long screwdriver so that’s not something the customer has to worry about after purchase, and (3) the inclusion of the second set of fan clips for those who want to run a push/pull fan setup.

The included Kaze Flex fan runs at a rather low RPM of 1,200, however, this results in superb noise levels. The Kaze Flex also has the benefit of rubber corners to allow isolation which prevents any vibrations at the contact point between the fan and heatsink.

Performance-wise, the Mugen 5 remains neck-and-neck with the other single-tower heatsinks while also being one of the quietest coolers in my entire testbed. The Mugen 5 Rev. B comes in at $48.99 on Amazon, which seems around the standard price for good heatsinks nowadays.

Overall, there’s not a real downside to the Mugen 5, just a ton of pros: Good price, decent performance, fantastic noise level, wide-ranging RAM support, and the list goes on.

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– Matt T. Green (MattNo5ss)

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Scythe's Mugen 5 Rev. B CPU heatsink sports compatibility with all current CPU sockets from Intel and AMD. The Mugen 5 is a typical single-tower style heatsink with one fin stack, as opposed to their dual tower FUMA heatsink or much larger Ninja 5 heatsink.

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