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AMD AM4 Ryzen Motherboard Buyer's Guide (Page 5)

By Steven Bassiri from Jul 3, 2017 @ 7:50 CDT

The Voltage Regulator Module

The AM4 platform requires many voltage regulator modules (VRMs), which takes the 12v (or 5v in some cases) and reduce it down to below 2v for different components. The most important VRMs are for the CPU (it gets two), and then memory, chipset, and so on. The CPU requires a Core and a SoC VRM right near the CPU socket. They usually use the same components as they provide power for the same part, but at different voltage and current levels. The CPU Core VRM is more important than the SoC, and when I talk phase count for the CPU, I will use a number such as 8+4, which means there are 8 phases for the Core VRM and 4 for the SoC section of the CPU.


Most people figure that more phases are better, and that might be true in some cases, but component selection is equally important. Different VRM control chips, known as pulse width modulation (PWM) controllers, offer different technologies that can improve high current performance, optimize power saving performance, offer more precise voltage control, and offer more overclocking features. Different power stage components from the MOSFETs (power and efficiency), chokes (power and noise), and capacitors (power and noise) range in quality and performance, and act as the body of the VRM instead of the brain (PWM controller). Both of these motherboards are using the International Rectifier IR35201, one of the most popular overclocking-centric PWMs, and both are using the same 4+2 phase configuration doubled to 8+4 phases.

However, while the one on the left uses higher quality IR3555 (60A PowIRstage) MOSFETs while the one on the right uses Texas Instruments CSD87350 (40A NexFET) with slightly lower ratings. Both are best in class and some of the best you will find on an X370 motherboard. However, the motherboard on the left has a slightly better filter stage, with capacitors rated to 10K hours rather than 5K on the right, and a different type of inductor. Will these VRMs let you overclock significantly further than those we are about to see? Probably not, but if you have the motherboard for the long haul and you need it to last a very long time with a 4.1GHz overclock on all cores, then you will want a higher quality VRM that runs a bit cooler and not at the limits of its components.


The VRM on the left uses a Richtek PWM while the one on the right uses an Intersil. Both PWMs are decent, and both offer overclocking features and will get the job done. The VRMs pictured before are on very expensive X370 motherboards, while the ones pictured above are from mid-range motherboards. The configuration on the left uses discrete MOSFETs for each power stage, while more integrated power stage components are located in the VRM in the image to the right. Each VRM phase must use one high-side and one low-side MOSFET, but there are also packages that integrated both and even a driver into a single chip.

These integrated solutions are a bit more expensive and can offer better performance, but not in all cases. The more discrete configuration on the left is actually better than the more integrated one on the right, mainly because of phase count. There is no easy way to compare if one VRM is better than another, but in our motherboard reviews, we do thermal imaging of the VRM and breakdown the parts. In this industry, you typically get what you pay for, but it's not a bad idea to read a review or two that goes over the VRM.

Clock Generators


Some motherboards have dedicated clock generators. The reason for their existence is because you cannot change the CPU's bus speed without one dedicated to changing the bus speed. Increasing the bus speed can help with memory overclocking above 3.2GHz as some multipliers are better tuned that others. Now that AMD has unlocked higher memory multipliers that might change, but some lower multipliers might still be tuned better, and bus speed change could still be useful for memory overclocking. There are not many motherboards with these clock generators, but you can easily spot them as large black squares, plus they will definitely be in the marketing.

Overclocking Features


I think the handiest overclocking feature is the POST Code display, which outputs a hexadecimal pair to match against stop codes in your motherboard's manual. Not all motherboards have it, but it's very useful in diagnosing hardware or overclocking boot failures. Some motherboards might offer boot LEDs instead of a POST code display, and they can tell you if the CPU, RAM, VGA, or boot device is holding up your booting. Some motherboards also offer the typical power, reset, and clear CMOS buttons, others offer more advanced OC features such as LN2 mode, re-try, slow-mode, or safe-boot.

Memory Support

The faster you can run your memory with Ryzen, the faster you can also run the Infinity Fabric that connects the different processor units. However, Ryzen memory overclocking has proved to be a bit difficult depending on density, IC type, and number of DIMMs.


AMD officially recommends the configuration above for speed of DIMMs vs. their rank. Single rank means a memory module with memory on only one side, and dual rank means memory chips are on both sides. Dual rank memory does tend to provide better performance, but it cannot overclock much higher on the platform as of now. I strongly recommend you look at your motherboard's qualified vendor list when it comes to picking a memory module. Almost every brand keeps an active list of compatible memory kits for each motherboard.

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