Key Takeaways
- The L/H switch stands for “Low/High” and controls the maximum fan speed, with high mode providing better cooling performance.
- Combining high mode with a custom fan curve maximizes cooling performance while keeping noise levels relatively low.
The AMD Wraith Prism is one of the coolest stock CPU coolers—it’s actually great at keeping your processor cool and has awesome RGB. But, if you’ve recently acquired or already have it, the Prism hides a secret you should know about.
Where’s the L/H Switch, and What Is It For?
If you’ve installed the Wraith Prism correctly, you’ll find the L/H switch is on the bottom right side of the cooler. L/H stands for “Low/High,” and it controls the maximum fan speed. The switch is set to low from the factory, as the fan can get very loud in high mode, and the cooler still does a great job. But if you’re like me, you’ll switch it to high before you’ve finished reading this sentence.
The switch is somewhat hard to reach, especially when the cooler is already installed. You can still flip the switch using your fingernails, so avoid using any tools that could get stuck or damage your components.
High Mode Is Cooler, but Should You Make the Switch?
The difference between the low and high maximum speeds is substantial. The fan spins up to around 2,000 RPM at low and 2,800 RPM at high. That’s a difference of 40% for those counting at home, and you can bet that it’ll shave off more than a few degrees at a maximum load.
Whether you want to switch it to high depends on how much you favor peace and quiet in your gaming room. If you’re a headphones user, don’t care about noise, or are just used to hearing fans because you live in a hot climate, switch it to high. Also, if you’re an overclocker, you’ll appreciate the extra cooling headroom in high mode.
But if you also use the computer for work, are happy with your current CPU temperatures, or just don’t need the extra cooling headroom, then you can keep it on low. A good rule of thumb is that as long as you’re happy with your computer’s performance, there’s no need to mess around with it.
Here’s the thing—the AMD Wraith Prism gets obnoxiously loud, even when it’s spinning at max speed in low mode. It’s a relatively small fan that has to push a lot of heat away from the heat sink, so it compensates by spinning extra fast. When you switch it to high mode, and the fans spin up, it starts to sound like a large, angry mosquito. That’s why I’d go as far as to label high mode as an overclocking feature for enthusiasts.
Still, the Wraith Prism in low mode is miles better than the horrible stock Intel cooler, which can hardly keep up with the processors it ships with. And it rivals many decent aftermarket coolers when the fan is in high mode. That’s because AMD went the extra mile by teaming up with Cooler Master, and you can thank them for implementing these types of extra features.
Combine High Mode With a Custom Fan Curve
You can actually squeeze out the best performance this cooler has to offer while still keeping it relatively quiet, at least when the extra cooling isn’t needed. Switch the fan to high mode so that it has the maximum headroom available, then use a custom fan curve to optimize the fan for noise levels. A fan curve tells a fan how fast it should spin and at which speed. You can do this in your computer’s BIOS or by using a program like SpeedFan.
Set your CPU fan to 100% when it goes above 70–75°C, and gradually drop the speed down at lower temps. You can go as low as 0% below 50°C, as your CPU can’t overheat at that temperature, and your PC will stay dead silent. Just be sure to experiment with this a little, as constant shifts in fan speed are as annoying as having the fan set to 100% all the time.
