What does it take to cool Ryzen 7700X? Part Two: Fractal Design’s Celsius+ S28 Prisma 280mm AIO Liquid Cooler

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Edited 3/18/23 : Added link to review of my results with this cooler on Intel’s i9-13900K at Boring Text Reviews

A black and white picture of the package containing AMD's Ryzen 7700x CPU, with the background behind it blurred
AMD Ryzen 7 7700X

Last week I posted my first article exploring how entry level cooling effects Ryzen 7700X with and overview of Iceberg Thermal’s G4 Silent air cooler. With today’s article we’ll be looking at how liquid cooling can improve potential performance thanks to Fractal Design, who sent us their Celsius+ S28 Prisma AIO for testing.

In the last article I mentioned how my past testing of coolers had focused on Intel CPUs because they were the most challenging to cool and also consumed the most power. Some of you may remember that when Alder Lake was released, I remarked that the thermal difficulty of cooling the 12900K was more difficult compared to prior generation products, and in turn most coolers were unable to keep the CPU under TJMax under the most intensive workloads.

Raptor Lake was even harder to cool, and as a result I had to change my testing methods because literally no cooler (at least, none that I had tested) was able to keep the CPU under TJmax under the most intensive of workloads.

Well, higher temperatures are no longer just an Intel thing – modern AMD CPUs are also designed to run at their peak temperatures during the most intensive workloads (they do, however, consume less power than their Intel counterparts).

As the manufacturing processes of CPUs continue to shrink their thermal density will also continue to rise – meaning that the difficulty of cooling processors in heavy workloads will only become harder in the future.

I have been interested to see how different levels of cooling performance effect both AMD and Intel platforms for some time. Thanks to our partner ASRock this is now possible – they sent a sample of their B650E Taichi for testing purposes. I will be taking a closer look at this motherboard in the future – but in the meantime check out reviews of this pristine motherboard on Funkykit & Tom’s Hardware.

Introducing Fractal Design’s Celsius+ S28 Prisma, a 280mm AIO Liquid Cooler

Swedish company Fractal Design is well known amongst PC enthusiasts, their recently released North computer case has been received well by the public and reviewers – winning the Editor’s Choice Award and a 5 Star review at Tom’s Hardware. I recently reviewed Fractal’s Celsius+ S36 Prisma (360mm), pairing it with Intel’s i9-13900K, and it was one of the best coolers I’ve had the pleasure of testing. Today we’ll be testing the 280mm version of that cooler with AMD’s Ryzen 7700X.

Packaging and Included Contents

Like most other AIOs on the market, Fractal’s Celsius+ S28 arrives in a box that has molded cardboard to carefully fit and protect the contents during shipping. The contents are also protected with plastic coverings.

The inner packaging of the Celsius+ S28 and the inner contents

The Celsius+ S28 comes with pre-applied cooling paste, a 280mm radiator and RGB CPU block, 2x 140mm fans, a user guide, and mounting for modern AMD & Intel platforms.

Mounting equipment for AMD & Intel Platforms
The Radiator and CPU Block of the Celsius+ S28 Prisma

AM4 and AM5 Installation

Installing Fractal Design’s Celsius+ S28 Prisma was very easy. Normally I would show pictures of the installation process – However, Fractal Design uploaded a 48 second YouTube video demonstrating this process that I feel would be more effective than any photos I would show you. Check out the video below.

…and here’s a photo of the S28 Prisma installed inside of DeepCool’s CK560WH Computer Case

Features of Fractal Design’s Celsius+ S28 Prisma

RAM ClearanceAll heights supported
Thermal CompoundPre-applied
Fin & Housing MaterialAluminum
Pump Bearing TypeCeramic bearing and shaft
Pump Speed800-2800 RPM in normal use, 3500 RPM during thermal protection mode that activates if liquid temperature is over 60°C
Pump Noise20 dBA
Radiator Dimensions143 x 30 x 324 mm
Compatible SocketIntel LGA 1700, 1200, 1150, 1151, 1155, 1156, 1366, 2011, 2011-3, 2066
AMD AM2, AM2+, AM3, AM3+, AM4, AM5, FM1, FM2, FM2+
Manufacturer Warranty5 Years

PWM and Auto (Silent) Modes

Arctic’s Celsius+ coolers can switch between silent mode and PWM mode with the flick of a wrist. The Auto (Silent) mode impressed me when I tested the S36 for Tom’s Hardware (the bigger brother of the S28), I found that it offered total cooling capacity equal to the highest end air coolers while remaining perfectly quiet.

Full Copper CPU plate with pre-applied thermal paste

30mm Radiator with Built-in PWM & aRGB hub

The included radiator measures 30mm, or just over an inch in thickness. This should fit all but the most cramped of cases without issue. Fractal Design’s Celsius+ S28 Prisma was designed to enable a clutter free installation, and includes a PWM & aRGB header hub to this end.

140mm Fractal Design Prisma AL-14 PWM Fans

2x Prisma AL-14 PWM Fans

There’s more to a cooler than just it’s heat sink, the fans paired with a cooler have a huge impact both total cooling potential and noise levels – included with the Celsius+ S28 Prisma are 2x Prisma AL-14 PWM 140mm Fans.

Model Prisma AL-14 PWM ARGB
Size140 x 140 x 25 mm
SpeedPrisma AL-14 PWM ARGB
AirflowUp to 103.9 CFM/176.44 m3/h
Static PressureUp to 2.38 mm H2O
Noise LevelUp to 34.1 dBA
BearingLong Life Sleeve (LLS)
Low (0-20%) PWM speed500 RPM
Low PWM noise level15.1 dB(A)
Low PWM airflow31.67 CFM
Low PWM static pressure0.44 mmH2O
Connector4-pin PWM
Rated LifespanOver 100,000 hours

Test Platform Configuration

Test Configuration
CPUAMD Ryzen 7 7700X
MotherboardASRock B650E Taichi (sampled by ASRock)
Computer CaseDeepCool CK560WH (sampled by DeepCool)
Storage1TB Kingston Fury Renegade
GPUIntel ARC A770 LE (sampled by Intel)
RAM32GB (16gb x2) Crucial DDR5-4800 (Sampled by Micron)
Coolers TestedIceberg Thermal IceSLEET G4 Silent
Fractal Celsius+ S28

As I have limited time to test coolers on this platform, today’s article will be more of an overview than a typical review. For thermal results, I’ve tested the CPU in three configurations: At the default PPT, with a 95W PPT enforced, and with a 75W PPT enforced.

This review will highlight performance when using an AMD Ryzen 7700X CPU. If you’re interested in performance results with Intel’s Raptor Lake i9-13900k those results are available at my review of this cooler on Boring Text Reviews.

Default (105W) PPT

At the default PPT of 105W, the most intensive loads can be difficult to cool and often result in the CPU running at TJMax. As such, we’ll be looking at 3 Metrics in this situation: Noise levels, watts cooled, and clockspeeds maintained.

Some of y’all might notice that the graph starts at 36 instead of zero – this is because my sound meter cannot measure noise levels lower than 36 dBA, effectively making it the noise floor for our testing purposes.

In PWM mode at full speed the AL-14 fans can bring noise levels up to 48.5 dBA. This isn’t quiet, but it isn’t loud either. In Auto mode – or as I prefer to call it: Silent Mode – the total system noise levels were supremely quiet, measuring at 36.4 dBA – which is basically as low as I can reliably measure. It’s quite possible that the noise levels are truly lower, and that my sound meter is incapable of properly measuring it’s noise output.

While the comparison results above are limited, below are results at full fan speeds from my Intel thermal testing rig. Keep in mind that these results are not 100% comparable due to configuration differences.

In this situation where the CPU hits TJmax, another metric which is useful to compare cooling performance is the total watts cooled by the cooler.

From the limited testing above, we can see that higher end cooling solutions will have limited returns when paired with AMD’s Ryzen 7 7700X. Fractal’s Celsius+ S28 was only able to cool 17w more (14.7% higher) than IceBerg Thermal’s entry-level IceSLEET G4 Silent in this scenario.

How well does that 14.7% higher power consumption while using stronger cooling translate into improved performance? Not very much at all. At 19298 vs 18774 points, we’re looking at 2.7% total increase in performance overall. This is a much smaller gap than I would have expected from Intel’s i9-13900K, where I’ve seen a 6% drop in performance using basic air cooling.

In this authors opinion, where Fractal’s AIO shines is in it’s Auto (Silent) mode. While technically it cools a few watts shy of Iceberg Thermal’s entry level air cooler in this mode, it does so while running completely silently.


Imposing even a minor power consumption limit on AMD’s Ryzen 7700X reduces cooling difficulty dramatically resulting in the ability to easily to cool the CPU under TJMax (95c), as such in these situations the total noise levels are more important. It’s also important to test in these TDP restricted situations, because most “real life” workloads will not push the CPU to it’s limits.

The advantage of liquid cooling shows in the acoustic results of this wattage limited test. In both the Auto Mode which is designed for complete silence AND the PWM mode in which the motherboard aims to maintain a lower CPU temperature, Fractal Design’s S28 Prisma runs quieter than IceBerg Thermal’s G4 Silent – an air cooler also designed for low noise levels!


Lowering the PPT to 75W further reduces the cooling difficulty, bringing temperatures down to 40.9C over ambient in PWM mode and 50C over ambient in Auto (Silent) mode. Total system noise level is very quiet in the PWM mode, but at 38.2 was curiously just as loud as in the 95W mode.

Thermal results in this scenario are interesting, with the Celsius+ S28 in PWM mode maintaining an 8 degree lead over comparison air cooler.


In my opinion, Fractal Design’s Celsius+ line of coolers is one of the best on the market. The PWM mode offers high potential cooling capacity for workloads that need extra power, while the Auto (Silent) mode offers whisper quiet operation and cooling capacity capable of handling all but the most extreme loads without throttling.

For it’s whisper silent performance with good total cooling capacity in it’s Auto (Silent) mode combined with the ability to switch to stronger cooling capacity in it’s PWM mode, I am awarding Fractal Design’s Celsius+ S28 Prisma 280mm AIO our Gold Tier Award. You can’t go wrong with this cooler.

If you’re interested in the results of this cooler with Intel’s i9-13900K, check out my companion review of this cooler at Boring Text Reviews

Fractal Design Celsius+ S28, a 280mm AIO Liquid Cooler
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