Review Cooler Master ML360 SUB-ZERO (+ Overclocking Core i9-10900K @ 6 Ghz )

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February 23, 2021

Review Cooler Master ML360 SUB-ZERO (English Version)

CRYO Intel

Cooling in a computer is usually designed to keep components (especially processor) within their thermal limit, which usually translate to operation above room temperature. Operating the processor below room temperature or even reaching sub-zero temperatures (below 0 degrees) will generally require an ‘extreme’ cooling solution such as Dry Ice and Liquid Nitrogen. Unfortunately, since it’s passive ‘active’ cooling solution, it is extremely difficult to use in a day-to-day context. It is only used by extreme overclockers for testing or benchmarking (breaking records).

Cooler Master in collaboration with Intel tries to present a new concept for processor cooler which is able to cool the processor operating below room temperature, and yet safe to use 24/7. Meet the Cooler Master MasterLiquid ML360 SUB-ZERO powered by Intel Cryo Cooling Technology.

A Closer Look: Cooler Master ML360 SUB-ZERO

What is ML360 SUB-ZERO?


As seen above, the physical form of the ML360 SUB-ZERO is no different from an AIO (All-in-one) Watercooling unit with a 360mm radiator. The difference is that this unit can produce temperatures in the sub-ambient range (below room temperature), even sub-zero (below 0 C).

ML360 SUB-ZERO Key Components: Thermoelectric Cooling (TEC)

One of the main components that enables the ML360 SUB-ZERO to operate under room temperature is the Thermoelectric Cooling (TEC) module (also known as ‘Peltier’ module).

TEC ResearchGate1
TEC illustration (source:


In simple terms, a TEC is a plate that is able to transfer a certain amount of heat from one side to the other when it gets an electric current flow. When the TEC is running, one side will be very hot (hot side), one side will be very cold (cold side).

In certain scenarios, even the cold side can freeze achieving temperature below 0 C. The use of this TEC module is one of the key components that allowed the ML360 SUB-ZERO to work below room temperature.

CM V10 Heatsink
Cooler Master V10 – Heatsink with TEC


The use of TEC component on a thermal solution for PC is nothing new. There have been quite a number of PC enthusiast users who have tried to use TEC in the past. It is either via ready made products (such as the Cooler Master V10 Heatsink), or through certain modifications.

Unfortunately, TEC has several fundamental problems, such as:

  • TEC can only transfer heat optimally within a certain capacity. This value is called QMax, commonly measured by the Watt rating.
    Generally, it takes a TEC module with a power rating higher than the heat output / TDP of the component it handles. For example, if a processor has a TDP rating of 100W, a TEC module rated above 100W is needed for optimal result.
  • When the TEC module is less powerful than the cooled components, cooling will be less than optimal (or even worse than a normal heatsink fan)
  • On high power TEC modules, the cold side can operate below 0 C, resulting in condensation that could potentially cause damage.
  • On the hot side at TEC, the heat that must be dissipated is a combination of the component heat output and the TEC Module. For example, if a processor has a TDP rating of 100W while the TEC is rated at 150W, then the setup has to dissipate 250W on the hot side. This is quite difficult for ordinary heatsinks to handle and usually require more powerful cooling like watercooling.
  • TEC will increase the total system power consumption, making the total power consumption relatively higher compared to standard coolers.
  • There are known attempts to reduce the weakness of TEC, such as creating a controller to make the TEC operate in a certain temperature range or at a certain power, but this solution is rarely used in consumer class devices.

To deal with some of these weaknesses, the ML360 SUB-ZERO uses Intel Cryo Cooling Technology.


What is Intel Cryo Cooling Technology?

Intel Cryo Cooling is esentially a combination of hardware, software, firmware to produce cooler with tightly controlled sub-ambient temperatures. The ML360 SUB-ZERO not only uses the TEC in a ‘traditional’ way, but uses this TEC in combination with some tight controls provided by Cryo Cooling technology.

With Intel Cryo Cooling technology, the TEC module in the ML360 SUB-ZERO cooler will operate dynamically, adjusting the output of its TEC based on the conditions of various inputs and sensors, such as:

  • CPU Power Sensor
  • Temperature sensor (from the CPU, and also from the cooler unit)
  • Humidity sensor (to calculate the dew point)

With this kind of telemetry and control, the ML360 SUB-ZERO cooler will try to reach a sub-ambient temperature above the dew point temperature to prevent condensation, while calculating the power output of the CPU so that the TEC is operating in the most power efficient way.

The expected result is that the CPU operating at a controlled sub-ambient temperature without the risk of condensation, thus improving overclocking capabilities.


Intel Cryo Cooling Requirement

In order to run the Cryo Cooling system correctly, in addition to needing a cooler that is compatible with the Intel Cryo Cooling standard, we will need these following components:

  • Intel 10th Gen ‘Comet Lake’ K-Series LGA1200 CPU
  • Z490 motherboard with certain BIOS version that supports Intel Cryo Cooling
  • Intel Cryo Cooling software, which currently only runs on 64-bit Windows 10 OS

We will also need to consider some other aspects, such as:

  • A PC chassis that has enough space
  • An adequate Power Supply (The recommended value from Cooler Master is a minimum of 750W, depending on system configuration)

Additional notes about Cryo Cooling Compatibility:

As a side note, considering that Intel Cryo Cooling is specifically designed for Intel systems, the ML360 SUB-ZERO only has the mounting for Intel system (LGA1200). Although users can modify the mounting to make this unit compatible with other systems like AMD, please note that this cooler can only function normally when the Intel Cryo Cooling software is running, so the use on systems other than those compatible with Intel Cryo Cooling is not recommended.


Now, we’ll take a closer look of this ML360 SUB-ZERO.



The Box & Equipment

Inside the Box


FOTO DSC00711B Manual
Manual book


FOTO DSC00714 Unit
The Unit


FOTO DSC00715 pump
Dedicated Pump


FOTO DSC00717 Block
8-pin PCIe Power Connector for the TEC module (also for Control Unit & Sensor)


FOTO DSC00718 Surface



FOTO DSC00725 Backplate
Install the backplate


FOTO DSC00727 Mount


FOTO DSC00727B Shroud
The black shroud that will minimize the contact between the area around the socket and the outside air


FOTO DSC00735 FanConnector
Install the radiator fan connector (there are three fans) on the motherboard, don’t forget to also install the power pump connector


FOTO DSC00736 Tec Power
IMPORTANT: Install the 8-pin PCIe power connector!


IMPORTANT: Attach the USB connector on the block to the motherboard, it will allow the Intel Cryo Cooling software to be installed


                                                      FOTO DSC00738 TEC USB2



Operation Mode – CRYO vs UNREGULATED

Last Step : Intel Cryo Cooling ‘Cryo’ mode MUST be enabled for normal operation


As seen above, after installing the software, the cooler will operate in Standby mode – which means the TEC will be turned OFF. The unit in standby mode can withstand light loads, but can NOT handle a heavy load condition. At this point, you need to select one of the two available modes of operation: Cryo Mode or Unregulated Mode.

In Cryo Mode, TEC will operate in a controlled-manner, where TEC will only operate according to CPU load. The TEC will turn on to keep the CPU temperature below room temperature, but still above dew point.

In addition to Cryo mode, the Unregulated mode will operate the TEC at full power, potentially causing the processor to enter the SUB-ZERO temperature at idle, as you can see in the image below:

The waterblock cooler sensor reads Minus 8 C in unregulated mode at idle


Unregulated mode may be used for overclocking experiments, but considering the risk of condensation in unregulated mode, for normal day-to-day operation, the recommended mode is Cryo Mode.


Clearance Check

Here is an overview of the unit once installed, still leaving enough space between the tubing and our RAM module.

FOTO DSC00732 RA Clearance



Testbed Specifications


The following are the specifications of the PC that we use for testing:

  • CPU : Intel Core i9-10900K
  • Motherboard: GIGABYTE Z490 AORUS MASTER
  • RAM : G.Skill TridentZ DDR4-3600CL16 RGB
  • VGA: GeForce RTX 2080 Ti
  • SSD: ADATA SX6000 nvme 128GB
  • PSU: Corsair AX1200
  • Case : No Case, Open Bench Table (Ambient 25 – 26 C)


Comparison: EK-KIT S360 Custom Watercooling

To provide a comparison, we used a custom watercooling set from the EKWB, the EK-KIT S360.



The Scope of the Test

Apart from briefly discussing the unit installation and operating mode, we will conduct a couple tests to see the system temperature and power in various scenarios, and see how overclock-ability improves (if any). We’ll use monitoring software such as HWINFO to check the processor temperature.

Let’s begin!


Test result

Test 1: Temperature in various scenarios


It is clear from the first test above, at light loads like the CPU-Z 1T benchmark, the ML360 SUB-ZERO is providing better temperature compared to our custom 360mm watercooling. However, on heavy loads like the Blender bmw27, it appears that the TEC on the ML360 SUB-ZERO fails to maintain the processor temperature as well as our custom watercooling.

On the next test, we’ll take a closer look at the bmw27 Blender test, because there are clear indications that the power / TDP setting of the processor has a significant influence on the temperature characteristics of the ML360 SUB-ZERO.


Test 2 : 10900K – No Power Limit vs 125W Power Limit

On some systems, the Core i9-10900K can be operated without Power / TDP Limit, or following Intel’s 125W TDP stock limit.

We’ll see the temperature difference here :


It seems pretty clear that in ‘No Power Limit mode’ where the Core i9-10900K processor can operate at nearly 200W TDP, the ML360 SUB-ZERO is unable to keep the processor temperature to an ideal point at this heavy load.


Test 3: ML360 SUB-ZERO vs Custom Watercooling 360mm – 125W Power Limit


Under maintained load conditions where the CPU is operating at a stock power limit of 125W, the ML360 SUB-ZERO could have a much more reasonable temperature.

Even though the initial temperature is relatively high (when the Turbo Boost on the processor is still active), when the Turbo time is up and the processor returns to 125W Limit, the temperature on the ML360 SUB-ZERO can be equivalent to, or even better than, a custom 360mm watercooling!


Test 4: Total System Power


The TEC Module in the ML360 SUB-ZERO will consume a certain amount of power while operating. Added with the system loads, we find that the system cooled by the ML360 SUB-ZERO has a relatively large power consumption, especially during heavy loads.

The higher the CPU load, the bigger the difference between a traditional cooler and a TEC-based cooler can be seen. It is because the TEC is operating dynamically to match the CPU power output.


Test 5 : Overclockability

With temperature and temperature characteristics like this, we test the system for to check if there’s any extra overclocking headroom.

The following settings are running fairly stable on our system:

OC TVB setting

With the Intel XTU software, we overclocked our Core i9-10900K processor with some pretty aggressive settings. The processor is now operating at a maximum limit of 5.6 Ghz.

Keep in mind that the overclocking method we used in this article is focused on changing the processor settings at 1-2 cores light load. We didn’t change the processor speed at all-core loads (and even limit the processor at 160W to avoid overloading the TEC).

Here’s the extra performance we can get with these settings:


The benchmark result with the most performance increase after overclocking was the one with a less-threaded load. It is indeed just a small improvement, and most probably insignificant to most. But it has to be noted that this setting cannot applied with ambient coolers – even with the custom watercooling we used when we reviewed this processor a couple months ago.


Test 6 (BONUS): Maximum idle Clock OC – 6 Ghz in Unregulated mode

In unregulated mode with a cooler temperature of -8C, we are looking for the maximum point where our Core i9-10900K processors can operate (at idle condition). The results are as follows:

Screenshot 6Ghz Cryo 2

One of the cores of our CPU was able to clock at 6 GHz, before experiencing BSOD and crashes – Yay :p

This kind of speed is not stable for daily use, but this is the first time we have managed to graze the 6GHz figure with just watercooling. We’ve never seen any custom watercooling setup with an ambient temperature of 25C that could hit a result like this.



Overclocking Headroom & Performance Increase

With the ML360 SUB-ZERO in Cryo mode, our processor which has difficulty touching clocks above 5.4Ghz, can now operate at 5.6Ghz quite reliably without crashing thanks to sub-ambient temperatures. We did test this PC for around three days without being turned off, and we didn’t have any condensation around the socket at all.

As for overclocking, there is an increase in performance. But this is relatively small (under 10%), and only occurs in a ‘less-threaded load’ scenario. Due to cooler and TEC limitations, the all-core OC capability for heavy continuous load is somewhat limited. This might be useful for overclockers who is looking for maximum 1-2 Core performance, but may not be the case for users who run heavy-load rendering applications constantly, on processors such as the Core i9-10900K.

As an additional note, the increase in performance occurs due to manual overclocking that we do, it does not automatically occur by only installing the ML360 SUB-ZERO and Intel Cryo Cooling Technology. And the overclocking method we used (per-core) is also not very common, and requires more time for fine-tuning.

Temperature – Optimal at Low Load

As you can see, a TEC-based cooler like this can run the system at sub-ambient at low loads. It can even compete or even beat a custom 360mm watercooling. Unfortunately, there was certain difficulties to achieve optimal cooling at continues all-core heavy loads above 200W. The custom watercooling was actually better.

Power – Relatively normal at low loads, astronomical at high CPU load

With a TEC sensor that can communicate with the processor, power can be maintained at light loads to operate the TEC in power-efficient manner, but the power is doubled during heavy loads.

Some things still need improvement

Seeing that this cooler is the first generation that is released, there are also some things that still need improvement, such as the pump noise. It was quite noisy on a quiet system. And the pump is not controllable so far.

The software, Intel Cryo Cooling software did not automatically operate the ML360 SUB-ZERO Cooler in Cryo mode during start-up. At this moment, users are to manually select the Cryo mode at every reboots. We believe, a firmware update will fix this issue.



Intel Cryo Cooling technology like the Cooler Master ML360 looks is a cooling concept that was developed by Intel and cooler manufacturers to squeeze all the capabilities of the processor. This potentially provides a sub-ambient cooling concept that finally can be used safely 24/7, thanks to the strict control and regulation of the various components that communicate with each other.

As far as we know until the time this article was released, we has never seen a TEC cooling system that used telemetry from the processor to perform power and temperature regulation, to precisely keep the processor temperature above dew point, while keeping it below room temperature to maximize overclocking headroom.

Who is it suitable for?

From its operating characteristics, users who can get the maximum benefit from the ML360 SUB-ZERO would be the enthusiast users / overclockers who want extra overclocking headroom at light loads (<4 Core load). And it could be useful for gamers who want to squeeze out the last framerate on their cpu-bound game. However, this cooler is clearly not suitable for processor users delivering heavy loads continuously (e.g multi-core rendering with 200W + load).

Although this solution still has some limitations, we appreciate the efforts of Intel as well as their partners such as Cooler Master to present products like the ML360 SUB-ZERO in hopes of delivering a breakthrough and new standard in PC cooling.

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