Scythe Fuma Heatsink Review

Scythe has released its entry into the world of tandem tower heatsinks: the Fuma. Scythe heatsinks all have Japanese names, and the Fuma is no exception: it means “wind demon” in Japanese. It is powered by two Slip Stream 120 PWM fans. This sounds promising, but unlike the seemingly unending series of 160+ mm towers, the Fuma is less than 150 mm tall. Is this heatsink a wind demon or a mere dust devil? Let’s find out!

The Company and the Heatsink

Scythe is a Japanese company who seems to have been around forever, but in 2002 Scythe Co. Ltd. originally started in Akihabara Electric Town, located in Tokyo, Japan. About the Fuma, they say it is a downsized Mine heatsink, which sported a 140 mm fan. They spent “countless hours . . . testing and optimizing,” and:

formed a cooling device measuring 149 mm in height. To compensate the smaller surface, our researchers put a great deal of effort in tinkering a new baseplate design as well as redrafting the fin structure. . . fitting the scarce space conditions of small PC cases.

Twin-Tower-Design

Fuma is made of two towers connected via six heatpipes to the baseplate. The twin-tower structure prevents mutual heating of the heatpipes while enhancing heat dissipation to the fins. Combined with further improvements, cooling performance increases, whereas compact dimensions are maintained. Fuma is predestined for ultra-quiet cooling but is an ideal overclocking cooler as well – at a very reasonable price.

Compact height without loss of cooling performance

With its height of only 149 mm Fuma is lower than other high-end coolers currently available. This way, conflicts with side panels are avoided – even with smaller PC cases.

Flexible Fan mounting

It is designed for the use of up to three fans*. If two fans are used, flexible fan positioning is possible. . . . Furthermore, flexible fan mounting increases compatibility – conflicts with memory modules will be avoided

* 2 fans are included

Specifications

Packaging the Fuma

As is becoming more and more usual, the Scythe Fuma comes in fully recyclable cardboard packing. There are some lovely diagrams on the box. Standard marketing all around. These boxes look like they’re designed to hang on a rack in the Akihabara district or your favorite local store and purchased retail, on the spot.

Open the box and you see the fans protecting the heatsink. The Fuma, by the way, sits in a cardboard cradle. Under the fin stack cover you will find the accessories box sitting between the stacks.

Just to give you some proportion – those are 120 mm fans.

Looking at the Fuma

In the first picture, the heatsink is oriented as if the airflow is going from the bottom to the top, but this heatsink is designed for flexibility. Where you have tall RAM, you are able to orient the heatsink vertically so the airflow could run from top to bottom.

The next picture shows an oblique view of the tandem tower heatsink, this time without fans. The mirror-like fish on the top fins may be cosmetic, but it is attractive.

This view of the fin stacks shows the fins are fairly far apart, which is appropriate, since the fans included with the Fuma are known for their CFM, not their static pressure. You can also see where the fins are staggered, with half of them showing tooth-like leading (or trailing) edges. Finally, you can see the slot for the mounting bar.

A closer view of the slot shows the aluminum cooling nubs which adorn all Scythe coolers. These nubs also provide a means for keeping the mounting bar from sliding.

A closeup view of the Fuma’s bottom shows the cooling nubs again. You also get a different view of the sawtooth leading/trailing edges. The purpose of details like this is to provide turbulence in the airflow, improving the ability of the fins to transmit heat to the air.

Looking closer at the bottom shows the sticky protective film. Be careful of this, though. Once you pull it off, it loses its stickiness. You can also see the shape of the fins.

A closeup of the heatpipes shows they are fully covered by their fins. Whether pressed or soldered remains to be seen.

We can see the collection of small parts packaged with the Fuma. You will have to make do with the paper manual, though. A PDF copy is not yet available online. What you can see is the Y-cable for the fans – it sends only one RPM signal to the motherboard. There are also washers, TIM, and six fan clips! Indeed, Scythe provides you with the fixings for a three-fan extravaganza. We’ll have to take them up on that.

Mounting the Scythe Fuma

The Scythe mount comes in pieces. Here it is semi-assembled for you delectation. The nylon washers are loose. They go on threaded spacers which attach to the backplate. The mounting brackets are fastened to the spacers with flat-headed screws. And the entirety will be surmounted by the mounting bar, which is lying upside-down in front of the backplate. Follow the directions. Read the manual. Check your work. Those mounting brackets can go on upside-down. So can the mounting bar. Be careful. Read twice and assemble once.

The second picture shows the backplate from behind the motherboard. You will note this backplate is not position-agnostic. Orientation matters. Line it up with the socket screws in advance.

Now let us look at the flatness of the contact surface. In the first picture the blade is aligned with the airflow. Along this orientation the surface is not curved.

When the blade is set at right angles to the airflow a convexity appears. It doesn’t look like much. It is probably safe for my CPU – for a short time only. This means the heatsink will dwell on the CPU for a day, but no more.

The contact surface itself is very like a mirror. Those are the basement rafters you see reflected in the surface.

The second image shows the screw holding down the mounting bar. First of all, note, the mounting bar is oriented with the sides up – it makes a sort of U here. Second, note, the mounting bracket has the middle portion up where it is closer to the pressure screw. Finally, note, the pressure screw has no natural stop. You can really muscle on the mounting pressure if you try. Other manufacturers have special shoulders to stop the screws, with springs applying the pressure. Here, the screw applies the pressure.

Fans Clip to the Fuma

You can tell Scythe has been in the heatsink business a long time. Their fan clips work. You put the clips on the front fan, and with two fingers, it’s mounted. Getting the fan off is just as easy. Pull on the clips and they disengage from the fin stack, and off the fan comes. The second fan is where it gets – interesting. Those fin stacks are close together. If you put the clips on the fan and then try to slide it down, the clips interfere with movement, catching on the fins. So, don’t put the clips on first. Slide the middle fan down to the bottom. Then move it to the side and put on one clip. Then move it to the other and fasten the other clip. Now mount it. It’s surprisingly easy to do. One thing about the fins: you can see right through the front stack to the other side and spot the other clip there.

Second Image: Here is the Fuma with the third fan clipped to it. Notice the clip handles are far enough apart to avoid interference with each other. Smart engineering, that.

RAM

The pictures show you what happens when you put medium-tall RAM with the Fuma: the fan won’t go all the way down. You can also see, because of how the heatsink is mounted, the front fin stack sits just behind the RAM, so the fans in the middle and pull positions would not interfere with any RAM. However, those of you thinking of buying RAM should note these tests were performed with low profile RAM, which allowed me to use a front fan without moving it upward. There is no reason in these days of low voltage RAM for you to get RAM with tall heatsinks outside of aesthetics.

Setup for Testing

The Fuma was mounted with a 5mm diameter blob of TIM. The TIM blob was stiff enough to stand on its own. The TIM was allowed time to spread, and after a day the heatsink was tested with Linpack running AVX2 extensions. Linpack is the software Intel engineers use to maximize the heat produced by their CPU’s. Hence it is the best software to test overclocking. But Linpack runs in surges. When the temperature is graphed, you see ragged plateaus. In looking for cooling solutions, you want to know how well a heatsink cools those plateaus – you won’t care about the valleys. So the temps under 70 °C (the valleys) were ignored in analyzing core temps.

Each test run was 30 minutes in duration. The last 20 minutes of each run was measured, and the core temperature logs were analyzed in Open Office spreadsheets. An Intel chip reports its temps in one degree increments, so for best accuracy these reports should be averaged in aggregate. Here the core temps were measured once a second, resulting in 1200-line spreadsheets.

The digital thermometer measuring air temp reported its measurements in increments of 0.1 °C. The ambient temperature was measured every five seconds, resulting in 240-line spreadsheets. The mean ambient temp was subtracted from the mean core temps, resulting in a net temp for each run. Finally, the several net temps were averaged.

The Sound Pressure level was measured 1 meter from the heatsink, with the motherboard set vertically, the way it would be in your case. The ambient noise for this testing was 30.5 dBA. So the net SPL is the sound pressure level measured at 1 meter, less 30.5 dBA.

The Fuma was first tested by lightly screwing down the tensioning screws. This was the “low pressure” mount. After three runs the screws were tightened down to the limit my fingers would tighten the long shaft screwdriver. I could have closed my hand around the screwdriver and applied more pressure, but discretion was the better part of valor here, so finger tight was the limit. After three runs with two fans, I did two runs with three fans, with all three being PWM Slip Stream fans. Finally, I swapped out the PWM fans and put in three fixed-speed fans. Two of them were Slip Stream 120DB fans with nominal 800 RPM speed, and one was an older Slip Stream with a sleeve bearing, also nominally 800 RPM. The reason these latter two sets were only two runs apiece was because I wanted to get them done in time to remove the heatsink before it went a second day on the CPU. In any case, the net temps were 0.1 °C between the first two runs, and 0.2 °C between the second two runs.

Just to be clear: the only difference between the Low Pressure set and the High Pressure set was the applied pressure. The mounting was the same. The sole difference was some turns of the screwdriver on the tensioning screws.

Results of Testing

First of all, look down to the bottom of the chart. The Fuma, mounted with low pressure, still made it to the first level of cooling. I did not have to back off the voltage or the overclock to measure this heatsink’s cooling. This is indicative of major league performance.

Next, you should note the move from Low Pressure to High Pressure mounting improved this heatsink’s cooling by more than 11 °C. This is why a rival made his bitter comment about “some OEM’s” making heatsinks that applied more than Intel’s allowed pressure: the amount of pressure you apply in your mounting can make a huge difference in your cooling.

Third, note, adding a third fan only decreased the Fuma’s cooling by 0.6 °C. The net SPL only went up 2 dBA, but you could really hear those two decibels.

Finally, look at the performance of the three 800 RPM Slip Streams. This cooling was excellent, and you could barely hear it.

MSRP

$42.95

Conclusions

If you are careful not to “overtighten” this mount, the Scythe Fuma looks to be an excellent heatsink. How can a 149 mm tandem tower out-cool heatsinks much larger than it is? One suspects the convexity of the contact surface and the pressure applied by the mount had something to do with it. Heck, we already proved mounting pressure can make a huge difference in cooling performance.

Yet the Fuma really can cool well. And with its low MSRP, it will be a major bargain when it is released to the general public.

The fact is this heatsink can use 120 mm fans not known for high static pressure, this is a plus. You could use any fan with this heatsink – just reach into your collection. For heatsinks, I don’t trust sleeve bearing fans though. You would do better to get a pair of PWM Slip Stream DB 120 fans for it – the DB stands for Double Ball bearings. Or you could get three 800 RPM Slip Stream DB 120 fans and not hear the heatsink. The possibilities are endless.

So Scythe doesn’t want you to “overtighten” their mount. But leaving the issue of the unprotected screws aside, this is a really easy mounting system to use. You can see where a lot of thought has gone into this mount. Just don’t drop the screws.

The flexibility in setting up your fans is greatly appreciated. This means you can use this tandem tower heatsink even when you have high RAM.

Overall, then, this is a really cool heatsink.

Scythe Fuma Pros

• Excellent cooling performance
• Flexible fan arrangements
• Two PWM fans provided
• Easy mounting system
• Packing is fully recyclable
• Low MSRP

Scythe Fuma Cons

• You must take care not to overtighten your mounting screws
• Manual is not online – yet
• Screws are not attached to heatsink – easy to lose

Click the stamp for an explanation of what this means.

Ed Hume (ehume)