What are Motherboard Power Phases and VRMs?

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Motherboard Power Phases are basically a power control technique through which the motherboard provides clean, stable and consistent power to the CPU as well as to the RAM.

Essentially the power phases of a motherboard are determined by its Voltage Regulator Modules (VRM). Basically, the higher the number of VRMs the motherboard has the higher is the number of power phases it has.

The higher the amount of power phases the motherboard has, the more stable the system will run. This is of particular interest to the overclockers.

For this reason, on most of the high end motherboards featuring the likes of AMD X570 or the Intel Z590 chipsets, you will notice a high number of VRMs and power phases.

The amount of Power Phases your motherboard has, and the quality of voltage control each power phase provides is decided by the amount of Voltage Regulator Modules (VRMs) the motherboard offers and their quality.

IDEALLY, each VRM on your motherboard corresponds to one power phase, however, some motherboards use VRM doublers to increase the amount of power phases without increase the TRUE power phases.

A VRM consists of a MOSFET, Choke and a Capacitor each with their own function.

We will cover all of this in detail below.

To understand what are motherboard Power Phases and VRMs, let us start by looking at how the power is supplied to the PC.

The Power Supply Unit: 240/120V (AC) – 12V (DC)

The first stage in powering up your PC is the Power Supply Unit.

The PSU takes the voltage from the wall which is rated at 240/120V (AC) and then steps it down to 12V (DC).

12V is the required voltage for the motherboard to function. The 24 pin ATX connector that connects the PSU to the motherboard basically provides the 12V.

how to test motherboard without cpu 2
24 pin power connector for motherboard and 8 pin power connector for the CPU – both attach to the motherboard. They come from the PSU.

It should go without saying that having a good quality Power Supply Unit is essential for delivering the initial clean and stable 12V to the motherboard as well as to the rest of the connected components like the graphics card, the hard drives as well as to the airflow fans.

I recommend that you look for an 80Plus quality control certification on a Power Supply Unit before you buy it.

Also Read: Why is a Motherboard Important?

What are VRMs – Stepping Down from 12V to CPU Voltage

what is a VRM
VRM is a component that is found in many electronic devices including motherboards. It is used to step down and deliver consistent voltage. The better the quality of its subcomponents, the better would be its voltage consistency. Source Veto Electronics

Now that you are familiar with what a Power Supply Unit does, it’s time to get into the woods.

A VRM or Voltage Regulator Module is a component that works between your computer’s motherboard on one side and the CPU and the RAM on the other.

VRMs Step the Voltage Down to Levels Suitable for CPU and RAM

VRMs have the singular purpose of ensuring that the 12 volts from the motherboard is further stepped down to the 1.0 – 1.5 volts that are typically needed by the CPU and the RAM.

The exact voltage required depends upon the CPU and the RAM model and whether or not you have overclocked it.

Also Read: How to tell if RAM will work with your motherboard?

VRMs Also Regulate the Voltage and Protect the CPU

VRMs do not just step the voltage down, they also regulate it. Meaning they ensure that they deliver EXACTLY the voltage required by the CPU and not a millivolt high or low.

They also keep the power levels within acceptable values. That is, they ensure that sudden power spikes and dips do not damage the critical components.

With high voltages, you can burn the CPU and low voltages from a poorly made VRM can cause system instabilities and crashes.

VRMs are Often Overlooked

Unlike many other components of a motherboard, the VRM receives very little attention despite the critical role that it plays on a motherboard.

However, for stable system, a motherboard with a good Phase Power design is critical.

Where are the VRMs Located?

What are Motherboard Power Phases and VRMs
6 VRMs on the Right for the CPU – 2 VRMs on the Left for the RAM

The VRMs are located somewhere near the CPU and the RAM DIMM slots. They can be easily spotted by the chokes (they can come in varying sizes and shapes).

We will get to what chokes really are a little later.

But essentially, the VRMs are located on your motherboard.

Also Read:

How Many VRMs Does Your Motherboard Have?

There are two ways to figure out how many VRMs your motherboard has.

1. Visual Inspection

The first is using the good old visual inspection.

Manually count the number of chokes you can see next to the CPU socket as well as the DIMM Slots.

motherboard vrms labelled box phase power design w
This motherboard has a Power Phases/Stage Design of 6+2

The motherboard above has 6 VRMs for the CPU and 2 for the RAM. Hence, this motherboard has a Power Phase design of 6+2.

2. Motherboard Specification Sheet

Another method is to check the motherboard specifications. Often, older motherboards, particularly in the budget range, did not specify the amount of VRMs they had.

Fortunately, most of the newer motherboards highlight the amount of Power Phases they have, which in turn indicates the amount of VRMs they have. motherboard power stages specifications

Power Stages / Power Phases / Phase Power Design is a specification given to indicate the amount of VRMs on a motherboard.Motherboard specifications will tell you the Power Phases in the form of following numbers:

  • 3+1
  • 4+1
  • 4+2
  • 6+2
  • 8+2

The number preceding the + sign indicates the amount of Power Phases for the CPU. The number after the + sign indicated the Power Phases for the RAM.

Higher end motherboard have a higher number of Power Phases.

Important Note: Some Motherboards Use VRM Doublers – True Phases vs Doubled Phases:

There is a difference between TRUE Power Phases and Doubled Power Phases.

TRUE Power Phases are the number of phases actually supported by the Pulse Width Modulator (Pulse Width Modulator – the controller for VRMs) without using Phase Doublers.

Using Phase Doublers to increase the number of Power Phases of a motherboard is far less efficient than having TRUE Power Phases.

More on this below.

Also Read: When to Upgrade Motherboard?

So What are Motherboard Power Phases?

Each VRM represents a single power phase (Whether they are True or Doubled is another story). A power phase is the time period when a given VRM is turned ON and is regulating the voltage.

Therefore, the more VRMs the motherboard has, the more power phases it would have.

With more VRMs, each VRM has to be turned ON for a shorter period of time to regulate the voltage.

So for instance, if you have 2 VRMs, each would be turned on for half of the time. With 4 VRMs, each would be turned ON for 1/4 of the time.

VRM and PWM

As the time each VRM has to stay ON decreases, so does the heat generated by each VRM in its ON status.

This in turn improves how well the voltage is stabilized, how clean and accurately it is supplied to the CPU and how well it can perform particularly when your CPU is overclocked.

Also Read: How to check if CPU is overclocked?

One Caveat Though

The quality of the voltage regulation on the motherboard depends on more than just the number of VRMs and power phases it has.

The VRMs also need to be constructed with high quality and high tolerance materials, especially because of the heat that gets produced during their operation.

Components of a Motherboard Voltage Regulator Modules and the Power Phases

As mentioned, several different components work together to form a single Power Phase of a motherboard.

First you have the Pulse Width Modulator that acts as the prime controller for the the phases. Then you have the VRMs – the critical components.

Although the composition might be different, the VRM itself is made of three components MOSFET, Chokes and Capacitor.

In addition to that there can also be Phase Doublers which, as the name suggests, doubles the amount of Power Phases the PWM can support.

And finally, certain high end motherboards with large and powerful VRMs can have heatsinks.

1. Pulse Width Modulator (PWM) – The Orchestrator

The Pulse Width Modulator is a controller that directs which phase turns on at a given time.

IDEALLY each phase has a single VRM circuit. However, if Phase Doublers are used, then each phase on a PWM can be branched out into two.

The TRUE Power Phases of the motherboard are determined by the PWM.

A Periodic PWM Signal:

A typical PWM signal has consistent high and lows. The switching frequency between the high and low for a typical PWM is about 300KHz (300,000 times a second).

PWM Signal
A Typical PWM Signal

When the PWM signal switches ON (High) it sends a signal to the MOSFET of a VRM in the corresponding phase to turn on:

2. The MOSFET (Part of VRM) – Acts Like a Gate

MOSFET ACTUAL

This is short for Metal-Oxide Semiconductor Field Effect Transistor. It is further made of three parts, a gate, a drain, and a source.

MOSFET DIAGRAM

The GATE controls the MOSFET and the SOURCE is connected to the, well, source of power (PWM in this case). The DRAIN is where the current from the SOURCE flows to when the MOSFET is activated from the GATE – in this case it flows to the Choke (the next component in the VRM).

MOSFET works like a SWITCH, capable of turning on and off when a voltage is supplied or turned off at the GATE.

When the GATE receives a voltage from PWM at its allocated time in the cycle, it allows the power from SOURCE (PWM) to pass to the DRAIN (Choke).

3. The Choke / Inductor (Part of VRM) – Filters the Power

Chokes

This component can be easily spotted on a motherboard as it commonly looks like a metal cube. It is also known as an insulator.

It serves two functions. It can store and filter power. It does a lot to control the overall quality of the power.

Essentially, a choke takes the high frequency power coming in from the PWM and turn it into a stable 60Hz frequency usable by the CPU and other components.

The quality of a choke greatly determines how well the motherboard can withstand overclocking.

4. The Capacitors (Part of VRM) – Stores and Filters Power

capacitors on motherboard vrm

This is a common electrical component used in many electronic devices to store energy in an electric field and when required it can discharge this energy into the circuit they’re connected to.

For a VRM and it corresponding power phase, it serves the same purpose. It stores the current received from the choke and supplies just the amount as needed by the CPU, the rest is discharged or released via the ground.

In the process of supplying the energy to the CPU, the capacitor further filters out any spikes and ripples in the current. Thus smoothing out the quality of the energy delivered.

A good VRM will most certainly make use of high standard and high quality capacitors. These include capacitors branded as Solid Capacitors, Hi-C Capacitors etc.

Capacitor vs Inductors 101

Capacitors store voltage by storing energy in an electric field. Inductors store current by storing energy in a magnetic field.

5. Phase Doublers – Double Power Phases Without Doubling PWM Phases

This is one characteristic that is usually found on modern motherboards, particularly those that feature top of the line phase power design i.e 12+2, 14+2 etc.

Basically, the TRUE number of power phases for your VRMs are determined by the Pulse Width Modulator.

However, when a Phase Doubler is used, you can essentially take a PWM with 4 phases and double it to 8 phases. Motherboards that use this technique specify it on their spec sheets.

Phase Doublers
Gigabyte Z490 AORUS XTREME WATERFORCE has a 16+1 Phase Power Design HOWEVER, it uses phase doublers as indicated here.

The amount of VRMs you have will still equal the total amount of power phases your motherboard True or Doubled doesn’t matter.

PWM doublers
A basic look at Phase Doublers

True power phase VRM design is superior to doubled phased VRM design.

A doubled VRM design introduces a switching latency between phases thus reducing the overall efficiency of a VRM.

Doublers can reduce the overall cost of the motherboard and in certain situation they can be worth it. For instance if you have to choose between a 4+1 TRUE Phase Power design vs 8+2 DOUBLED Phase Power design, go for the latter.

6. Heat Sinks

VRMs get very hot during operation.

To reduce the negative impacts of high temperatures such as reduced performance, a heat sink is often used on some of the hotter parts of a VRM.

On more premium motherboards with large VRMs, bigger and better heatsinks are used.

Also Read: What are Front Panel Connectors on Motherboards?

Overclocking and Why VRMs / Power Phases Matter

The amount of VRMs, their size and the amount of power phases your motherboard has do not matter much to the general public.

They do, however, matter to the enthusiasts, gamers and professionals who want to overclock.

When you overclock, it directly puts burden on the VRMs as they now have to regulate a higher amount of voltage. Regulating a higher voltage also generates more heat.

In this situation everything from the number of phases to the size of the heat sinks and the quality of the capacitor starts to matter.

For this reason, on expensive motherboards, you will notice they have a high number of power phases and VRMs built with premium sub-components capable of withstanding a high amount of voltage and current.

You may also notice chokes having large heat sinks for dissipating the heat effectively.

Also Read: What CPU is compatible with my motherboard?

Conclusion

What are motherboard Power Phases and VRMs is a question often asked by overclockers and enthusiasts. This isn’t something that would matter much for an average.

Basically, a motherboard power phase is the time period in which a particular VRM turns on. Each VRM corresponds to a single power phase of a motherboard.

The VRMs have the sole purpose of taking the 12 volts from the motherboard and stepping it down 1-1.5 volts acceptable by the CPU and RAM.

The Power Phases and VRMs work together to regulate the voltage.

If you are an overclocker, you would want to have the best of the components for the VRMs as well as look for a motherboard with a high amount of power phases.

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Author:

Atif Qazi
Atif Qazi is the founder of PCGuide101. He is a digital nomad who loves everything PC. He is a PC builder, tech enthusiast, engineer, and a lover of single player lore-rich RPG games.

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