be quiet! Pure Rock Slim CPU Cooler Review 12

Introduction & Closer Look

Not all CPU coolers are designed to be big, megalithic towers capable of cooling Chernobyl; some are meant for smaller systems such as the one on test today. The be quiet! Pure Rock Slim itself has a small, but efficient design with an all-aluminium fin layout and black/silver colour scheme. The Pure Rock Slim is the smallest and cheapest cooler in the packed be quiet! CPU cooler range, but that doesn’t necessarily mean anything negative. In fact, the Pure Rock Slim was released to cater for those systems that have limited cooler space and doesn’t need anything ‘over the top’. The Pure Rock Slim comes in at a very reasonable £19.99 which puts it in the sub £20 price point; is the be quiet! Pure Rock Slim the best cooler under £20? Let’s find out…

Here we have the box…small, black and very informative!

Inside the box, we have a pair of clips for holding the fan on the heat sink as well as an AMD supported mounting mechanism. There is also a silence optimised 92mm PWM fan which features 7 blades. The Pure Rock Slim supports the following socket types:

Intel – 1150/1151/1155/1156
AMD – AM2/AM2+/AM3/AM3+/FM1/FM2/FM2+

Looking at the main tower, the Dark Rock Slim features 33 aluminium constructed fins with a small footprint. The cooler itself is 56.2 x 97 x 124.8mm in dimensions so this should easily fit in everything but the most hard-core of small HTPCs. This makes the Dark Rock Slim one of the agilest coolers on the market, but also one of the best value options based on the specifications.

On the base of the cooler, a thin layer of thermal paste has been pre-applied so unlike me, be careful not to get your fingers mucky! The Dark Rock Slim features 3 x 6mm copper heat pipes emanating from the copper base all the way through the fin array to provide an optimal cooling solution; it’s not direct contact, but for a cooler of this size and with a maximum TDP of 120w, it shouldn’t make much, if any difference at all.


To install onto an Intel LGA socketed motherboard, it follows the same click and push principle as the regular Intel stock heatsink does. Simply line the plastic clips up with the mounting holes and push through until you hear a click; the click signifies it’s in place, but make sure you listen out for a click on each mounting clip!

Here we have the Dark Rock Slim from be quiet! ready to be mounted onto our testing setup, but obviously the stock paste was cleaned off due to us using Noctua’s NT-H1 thermal paste; we have done this since the beginning of Play3r and we don’t intend to change now!


Heatsunk Specification:
– Dimensions (L x W x H), (mm): 56.2 x 97 x 124.8
– Total weight (kg): 0.36
– TDP (W): 120
– Fin material: Aluminum
– Base material: Copper

Fan Specification:
– Fan dimensions (mm): 92 x 92 x 25
– Speed @ 100% PWM (rpm): 2,000
– Air flow @ 12V (cfm / m3/h): 35.14 / 59.38
– Air pressure @ 12V (mm H2O): 1.67
– Bearing type: sleeve
– Motor technology: 4-pole fan motor
– Rated voltage (V): 12
– Input current (A): 0.32
– Input power (W): 3.84
– Connector: 4-pin PWM
– Cable length (mm): 220
– Lifespan (h / 25°C): 80,000


Since our previous cooling reviews prior to November 2016, we have decided to update the method accordingly for better and consistent results. It isn’t ideal running Prime95 for a prolonged period of time and if you get called away to do something, it could be left running for much longer than needed. Our new methodology involves running a very stressful multi-threaded performance benchmark called RealBench.

It should also be noted that the reason we omit acoustic/noise testing is due to an inaccuracy within the readings and method. To provide truly accurate readings, you need a lab setting with the same ambient noise on an hour by hour, day by day and week by week basis. As ambient noise can increase at different times of the day, we believe that it’s pointless providing noise testing if we can’t measure consistent and accurate data due to our office being a busy setting.

Test Setup

CPU – Intel Core i7 6700k – (4.2GHz at 1.25v & 4.5GHz at 1.38v)
Motherboard – ASUS Z170 Maximus Hero Alpha
RAM – Crucial Ballistix 3000MHz 32GB (4x8GB)
PSU – be quiet! 850w Dark Power Pro 11
SSD – Crucial MX300 525GB SSD
Case – Cooler Master Test Bench V2

Idle Testing Methodology

To test each cooler at idle, the minimum temperature is taken after leaving the PC with only start-up programs on Windows 10 being allowed to run for 5 minutes. After this, the minimum temperature with the core temperature being offset against the room temperature; thus achieving delta.

Load Testing Methodology

To load test, we run RealBench while selecting the heavy multitasking benchmark only. We run this a maximum of 3 times concurrently and the maximum temperature recorded is taken. This temperature is deducted from the current room temperature and our final delta temperature is provided.


As you can see from the above results, the be quiet! Pure Rock Slim is on par, Cooler Master Hyper 212 LED in most of the thermal testing, only being beaten at 4.5GHz (1.38v) by a single degree. This is fantastic performance for a small sized cooler, especially given the £10 price difference…which you could save and purchase a tube of high-quality thermal compound to replace the stock paste with.


It’s easy to see the market sector that the Pure Rock Slim fits into; those with space issues and of course, those on a tight budget too. The main plus points of the be quiet! Pure Rock Slim are that it’s cheap (£20 in the UK), it’s small and most importantly of all, it performs very well for such a small svelte CPU cooler.

With the 92mm be quiet! PWM cooling fan, the cooler is virtually silent and even at its maximum 2000RPM, it’s not as loud as you might imagine. Obviously, we would love to test acoustic performance, but due to not having a dedicated dead sound laboratory set up to do so, it would be absolutely pointless and those putting decibel meters up to it and taking readings, is pretty inaccurate, to say the least. That being said, you have to take my word for it that it’s quiet and I wouldn’t have expected anything different here from be quiet!

If I had to compare it to another cooler, it’s kind of an amalgamation between the Cooler Master TX3I (mounting/size wise) and the Hyper 212 LED (performance wise) CPU coolers. Of course, the Pure Rock Slim is around £10 cheaper than the Hyper 212 LED and with equal/similar performance, it represents a fantastic buy for those looking for a small, but decent alternative to a larger tower cooler.

There are absolutely no memory restrictions thanks to the small size and with high compatibility with most Intel sockets and virtually all of the relevant AMD ones, it’s a fantastic option. For £20, you’re not going to find a better cooler of this type and size wise, it’s a top option for those looking for a space and wallet saving option. The only negative is the fan clips are tricky to mount and if you don’t take great care, you can easily bend the thin aluminium fins.

If you’re looking for a tiny, but decent performing cooler and have a budget of up to £20, then make sure the be quiet! Pure Rock Slim is on your shortlist!

Big thanks to be quiet! for sending the Pure Rock Slim in for review.

 Awards image 7

  • Performance
  • Design
  • Value



– Exceptional performance for a cooler of this size/type
– Represents brilliant value for money thanks to the £20 price tag
– Runs particularly quiet
– Handles an overclocked Intel Core i7-6700K processor at 1.38v with no issues whatsoever
– Mounting system is easy to use


– Fan clips can be a little fiddly when trying to instal the provided fan on the Pure Rock Slim

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