Motherboard VRMs: What are Power Phases, and How Many Should I Have?

Motherboard VRM Power Phases Explanation

Often, motherboard product pages and online forum users mention a motherboard’s VRM and how many power phases it has. Being a somewhat technical topic, VRMs aren’t an easy topic to get into. So today, we will introduce the concept of the VRM and these so-called power phases as simple and straightforward as possible, so that you can easily discern what a motherboard product page is telling you (and when it matters).

The VRM: Important in Role, Yet Often Forgotten

On every motherboard exists a circuit near the CPU called the voltage regulator module, or VRM. The VRM’s job is to make the power from the power supply usable for the CPU, and help stabilize it, so to speak. Were it not for the VRM, your CPU wouldn’t even work!

The RAM also has a much smaller, simpler VRM next to the RAM slots. However, it’s usually only the CPU’s VRM that is focused on. Heavy RAM overclocking is done by few people, and RAM uses much less power than the CPU, hence why it’s often ignored.

Technical Stuff: Power Phases

A VRM is composed of separate power “phases”. Your baseline power phase is composed of two transistors, a “choke” and a capacitor. The transistors may or may not be covered by a heatsink, as they can get very hot and tend to be more temperature-sensitive. The chokes on modern motherboards usually appear as small black or grey cubes, which sometimes have a small differently-colored section in the middle. The capacitors are the other component, usually small cylinders in shape, next to the chokes.

Voltage_regulator_module_on_a_computer_motherboard

Photo by Dsimic

There are two separate groups of power phases in the VRM. One is used for the CPU cores, and the other is used by other parts of the CPU, like the integrated GPU. On your typical motherboard, the power phases used for the CPU cores (the ones we care about most) are found left of the CPU while the others are above it, but this isn’t always the case, especially for smaller motherboards.

As the number of power phases increases, the amount of time a given power phase is “working” decreases. For example, if you have two power phases, each phase is working 50% of the time. Add a third, and each phase only works 33% of the time, and so on.

VRM 4-Phase Diagram

4-Phase Example

If we assume the same components are used, then the more phases you add, the cooler each phase runs, the more power the VRM can put out, and the more stable the CPU’s voltages get. The more power your CPU uses, the hotter the VRM runs. Cooler operation improves lifespan of the VRM and reduces the risk of overheating, a potential concern for overclockers. A higher power output ability reduces the risk of overloading the VRM, which could make the system shut down or slow down the CPU. Better stability of power for the CPU can, to a limited extent, reduce the needed voltage for overclocking stability, improving CPU temperatures and theoretical lifespan.

Phase Quality

It is important to understand that more power phases does not necessarily mean a better VRM. The actual component choices in the whole VRM have big implications in running temperatures and how much power the VRM is capable of handling. The benefit to more phases is in the stability of the voltage the VRM outputs, while temperatures and the VRM’s power output ability are up in the air.

Four phases could very well be an overall better choice than eight phases if the components are sufficiently better. From a practical perspective, more phases is usually the better choice, but this is not always true, so it’s best to consider on a case-by-case basis.

Deceptive Marketing and Design

A fairly common design used by motherboard manufacturers is to double the amount of components used in each power phase, without actually doubling the number of power phases. Those who don’t know better would assume that you can count the number of chokes to count the number of power phases. In addition, and arguably more importantly, motherboard manufacturers often (but not always) use this design while also claiming a higher phase count. Though the number of power phases aren’t increased, the actual quality of the phases is still increased, greatly improving the VRM’s power output capability as well as operating temperatures.

Biostar B450MHC motherboardThis practice is misleading and not ideal compared to more actual phases, but it does still help. ASUS’ Z390 Maximus XI Hero and MSI’s B450M Mortar (Titanium) are examples of this design, though not of deceptive marketing. The Asrock Fatal1ty AB350 Gaming-ITX/ac, though, is certainly an example of a deceptive phase count claim using this design.

Even worse than this, motherboard manufacturers occasionally go beyond marketing doubled-component phases as more phases—by not even doubling all of the components, while still claiming a higher phase count. They might add another choke and maybe one transistor (albeit the more important one that handles the majority of the power) to give the appearance of more phases, but don’t add separate phases. Doing this makes any lies about phase count even more egregious, and (to a limited but not large extent) reduces the actual benefit. Gigabyte’s B450 Aorus M and Aorus Elite, Biostar’s B450MHC, and ASUS’ TUF Z370-Pro Gaming are examples of this design, though they do not have any phase count claims associated with them.

Both of these tactics considered, it’s best to not presume the power phase count based on the number of chokes you see on the motherboard, and to completely ignore phase count claims from motherboard manufacturers. The only way to really know the phase count is through analyzing the actual components (or, more accessibly, through seeking out a knowledgeable video-maker or writer online who has done this sort of analysis on the board or boards you are considering).

Conclusion

Ultimately, on systems with recent-generation CPUs, worrying about the VRM will mostly be relevant for those who want to achieve high overclocks, and not for typical users. As long as the manufacturer doesn’t list a certain CPU TDP as not being supported, you could use any modern CPU on a compatible-socket motherboard and run it non-overclocked without issue.

As a general rule based on currently-available motherboards, it’s unlikely you would encounter any significant setbacks with any decent four (actual) phase motherboard and a four-core or six-core CPU, nor with a six-phase motherboard and an eight-core CPU (at least as long as its cooling isn’t abysmal, like on the ASRock Z390 Pro4). And unless you’re trying to break overclocking records or you’re running a CPU with 16+ cores, there’s little practical benefit to high-end VRMs that might have over eight high-quality power phases. Temperatures can always be a concern, but actual temperatures will always vary between users and their hardware, while any effect on motherboard lifespan is unclear.

All that said, for most people, it’s not worth stressing out over the VRM. For us common users, it’s best to focus mostly on the features and maybe aesthetics that a motherboard provides. But by knowing this, you can make your choice more effectively for your needs.

Gigabyte B450 Aorus Elite motherboard