Big Typhoon Squared: Cooler Master GeminII Review

In this review we are going to test a new CPU cooler with 6 heat pipes used in its design. This Cooler Master product claims to leadership among all air coolers available in the market these days. Let’s find out how good this impressivesly-looking solution is from our new article.

by Sergey Lepilov
04/04/2007 | 03:05 PM

I will review and test a new cooler from Cooler Master today. It is called GeminII and the “II” stands for two identical fans which are a key feature of the product.


Frankly speaking, the idea to install two 120mm fans on a CPU cooler is not very new. You can recall Scythe’s Infinity and Ninja, for example. But those are tower-shaped coolers in which the large fans are placed in perpendicular to the mainboard plane. In the GeminII the fans are installed parallel to the mainboard and their airflow is directed downwards to its surface. And the cooler has also got a ingenious heatsink that I will examine shortly.

Package and Accessories

The new cooler comes in a cardboard box with an angular cut-out in one side through which you can see the heat pipes:

The sides of the box give you a lot of useful and not very useful info like a detailed specification with key features emphasized, a scheme of airflows, and a full list of supported CPUs (which could have easily been replaced with something like “All CPU types supported”):

Besides that, you can find an interesting diagram that claims the new cooler from Cooler Master to be 14°C more effective than the boxed Intel Core 2 Duo cooler.

The GeminII lies in a plastic tray that fits it perfectly:

This is both aesthetic and reliable at the same time. The following accessories are packed into a small separate box:

Note that the GeminII comes without fans included.

Design Features

The new cooler is designed in a simple but original way. It employs 6 copper heat pipes with an external diameter of 6 millimeters that come out of the copper base and distribute the heat flow in the aluminum heatsink. The same general principle is implemented in the Thermaltake Big Typhoon as well as in the Scythe ANDY Samurai Master that we have tested recently on our site. But let’s take a closer look at the GeminII:

It is large, isn’t it? The heatsink measures 175 x 124.6 x 81.5 millimeters making it the largest heatsink of all top-design coolers. It weighs 847g and is going to be over a kilogram with two fans installed.

Two parts can be seen in the aluminum heatsink. In the central part the ribs are soldered to the copper base:

The rest of the ribs just hang on the heat pipes. Take note that the bottom edge of this group of ribs has a wavy profile, making a wave in the place of contact with the heat pipes, i.e. in the place where the main thermal load is distributed.

I think this is a clever solution. There is a hole in the middle of the ribs soldered to the base which is meant to reduce resistance to airflow and to minimize the heatsink’s weight.

The whole heatsink arrangement is covered from above with an aluminum frame. The frame is secured with screws on the side ribs:

The frame has X-shaped bars to make it more rigid. I don’t think they are really necessary for that purpose because the sides are curved in and the load is low here, while these bars do create some additional resistance to airflow.

The heat pipes contact the heatsink’s aluminum ribs through the bottlenecks that were created when the plates were being hung on the pipes.

The copper base of the heatsink is protected against scratches with a piece of film. Don’t forget to remove it prior to installation.

The ends of the heat pipes are sealed and the pipes themselves contact the base by means of soldering.

There are almost no traces of soldering here. Everything is made very neatly.

The base finish is good:

It is flat as I verified by making a print of thermal grease on a piece of glass, but it might be polished better. Comparing it with other coolers, the base of the GeminII is finished better than the Thermaltake Big Typhoon’s but somewhat worse than the bases of coolers from Scythe or Titan.

Recommended Fans

I remind you that the GeminII heatsink comes without fans, but Cooler Master recommends using it with two 120mm R4-S2B-12AK-GP fans made by Cooler Master itself.

These fans are no different than others of their kind, though, so you can just use any other pair of 120mm fans you can find.

The fan speed is 1200rpm. The noise level is specified to be 19dBA, which is very low. This pair of fans does work very quietly. Running on a ball bearing, these fans have an MTBF of 4.5 years of continuous operation. The rest of the fan specification can be read from the photo of the box above or in the specs table.

Assembly and Installation Tips

Before you try to assemble the cooler and install it onto your mainboard, I suggest you take a look at the detailed step-by-step guide included with it. The guide has pictures illustrating the assembly and installation process, but one step seems very questionable to me. I’ll tell you about it shortly.

The GeminII can be installed onto every modern platform. Cooler Master regards LGA775 as the only modern platform for Intel processors (Socket 478 is not on the compatibility list). As for AMD processors, the GeminII supports Socket AM2, 754, 939, and 940. So, you have to attach an appropriate steel plate to the cooler’s copper bottom:

Socket AM2/754/939/940


But first of all, you insert fastening screws into the plate’s holes. Then you put on rubber rings to protect the mainboard from damage as you fasten the cooler on it:

Then you take the included guides and fasten fans on them:

After that you can put the fans on the heatsink and secure the whole arrangement with screws:

This is the order of proceedings according to the included installation guide. But I would advise you otherwise and that’s why. If you install the assembled cooler on the mainboard, you may find yourself unable to put it back into the system case because the GeminII is as long as 240 millimeters with two fans installed! So, I recommend you to install the heatsink without fans on the mainboard first. Then put the mainboard back into the system case. And only after that you can secure the guides with fans on the heatsink.

Installed on an ASUS P5B Deluxe mainboard, the GeminII looks like this:

As you understand, you’ll have to take the mainboard out of the system case to perform the installation. Moreover, considering the dimensions of the new cooler, it is simpler to turn the GeminII upside down and install the mainboard on it rather than vice versa.

So, you remove the protective film from its base, apply some thermal paste, put the mainboard down on it so that the CPU heat-spreader touched the cooler’s base, and finally fasten it on the reverse side of the mainboard with nuts and a special key.

Socket AM2


A back-plate is used for AMD platforms, but there is no such thing for Intel’s platform and the mainboard bends under the pressure, which is not good.

The base and the fastening frame are compact, so nothing prevented installing the GeminII on the two mainboards I used as you can see:

Socket AM2


Unfortunately, the cooler cannot always be oriented in the best possible way on AMD’s platforms (the mounting holes around LGA775 are symmetrical, allowing to orient the cooler just you wish). For the GeminII to be correctly installed on Socket AM2/939 mainboards it is necessary that the plastic fastening frame and the holes in the mainboard were parallel to the rear panel of the system case (or to the mainboard’s I/O connectors). This potential incompatibility is specifically mentioned by the manufacturer in the installation guide:

So, before purchasing the new cooler you should make sure it is compatible with your mainboard.

Finally, you put the mainboard with the heatsink back into the system case. Hang the fan guides onto the heatsink and attach the fans to the mainboard’s connectors.

Note that there are slits in the fan guides so that you could position the fans in the most effective way.

The frame with the fans can move to and fro by 70 millimeters.


The specifications of the new cooler from Cooler Master and of the recommended fans are listed in the following table.

Testbed and Methods

Not long ago we published a comparative review of super-coolers in which four well-known highly effective coolers were tested together with new products from Scythe and Enzotech (for details see our article called Scythe Andy Samurai Master and Enzotech Ultra-X Coolers vs. Overclocked CPUs). Considering that the testbed configuration hasn’t changed much since then, I won’t test many models but will limit myself to the best cooler of that earlier review, Enzotech Ultra-X. The results of the earlier test being available to you, you can easily compare the coolers from that test with the currently tested ones.

The coolers are tested on an open testbed as well as in a system case with the following configuration:

All tests are performed in Windows XP Professional Edition Service Pack 2. SpeedFan 4.32 is used to monitor the temperature of the CPUs, reading it from the CPU sensor. The AMD CPU is heated by S&M version 1.9.0b for 15 minutes at 100% FPU load. The Intel CPU is heated up by means of Intel Thermal Analysis Tool for 18 minutes (according to the method described in our article called Originality or Efficiency? Cooler Master Mars, Eclipse and Hyper TX Cooling Solutions Reviewed).

The mainboards’ automatic fan speed management is disabled for the time of the tests. The thermal throttling of the Intel Core 2 Duo processor is controlled with RightMark CPU Clock Utility version 2.2 (our processor begins to skip clock cycles on reaching a temperature of 81.5°C).

I perform at least two cycles of tests in each mode (TAT and S&M) and wait for 25-30 minutes for the temperature to stabilize during each test cycle. The maximum temperature in the two test cycles is considered as the final result (if the difference is not bigger than 1°C – otherwise the test is performed once again). Despite the stabilization period, the result of the second cycle is usually 0.5-1°C higher.

The ambient temperature was monitored by means of an electric thermometer and remained at 25.5°C during the tests.

Thermal Performance

The CPUs at my disposal were overclocked to the last drop of juice during this test session. The AMD Athlon X2 3800+ was overclocked from its default clock rate of 2000MHz to 2860MHz (a frequency gain of 43.0%) at a 286MHz clock-gen frequency and with a core voltage increase to 1.5625V. The Intel Core 2 Duo E6400 stepping B2 processor was overclocked from its default 2133MHz to 3550MHz (a 66.4% frequency growth) with a core voltage increase to 1.475V.

So, the Cooler Master GeminII has got a strong opponent and difficult test conditions. Let’s see if the new cooler can stand any chance against the absolute leader of our earlier test. There are only two coolers so I can put all the numbers into one diagram:

There’s nothing much to comment upon. We’ve just got one super-cooler more. The new product from Cooler Master is a mere 1-2°C worse than the Enzotech Ultra-X, which is just an excellent performance. You can take a look at our previous testing when the Ultra-X left no chance to such monsters as a Scythe Infinity with a couple of fans, Zalman CNPS9700-Cu LED and Thermaltake Big Typhoon. And here, the Cooler Master GeminII almost equals the performance of today’s most efficient cooler on CPUs that are overclocked even harder. Of course, the Ultra-X can be made to use a higher fan speed and win some 3°C more, but this would make its noise uncomfortable.


Our today’s tests indicate that overclockers have got another very effective and very quiet air cooler. The Cooler Master GeminII is already selling at a price not much different from the recommended one.

There are only two drawbacks about the new product: no fans included into the package and its limited compatibility with mainboards for AMD processors. The former drawback can be solved easily, but the latter is more serious. I hope the manufacturer will perfect the Socket AM2/939 fastening in such a way that the cooler could be oriented on the CPU socket in the best possible position.

Big weight? It’s not a problem as the GeminII uses threaded fastening through the mainboard which just can be more reliable. The mainboard has to be taken out of the system case to install the cooler, but you have to do the same with every super-cooler, except for Scythe’s (but I should add that the GeminII lacks a back-plate for LGA775 and the mainboard bends under the pressure). Size? The cooler fits into the system case perfectly and does not press against the components around the CPU socket. It does not exhaust hot air outside, but its design just doesn’t imply that.

The rest are indisputable advantages. The GeminII is highly effective and very quiet. It cools the near-socket space on the mainboard. It is not more expensive than its opponents, even including the cost of two fans. And it is already available for purchase! Very good news!

Where could the GeminII progress further? I would suggest the following:

So, I think there is still some work Cooler Master’s engineers might do to make this super-cooler even better than it currently is.