VRM stands for Voltage Regulation Modulator. It makes sure your GPU (or CPU) gets the required power at a consistent voltage. A low-quality VRM can cause many issues including shutdowns under load, poor overclocking capability and even reduce the life-cycle of your processor.
How do VRMs Work
A modern PSU supplies 12 volts of power to the motherboard and graphics card. However, CPUs and GPUs are sensitive and can’t withstand that kind of voltage. That’s where the VRM comes into the picture. It steps down the incoming 12-volt power supply to 1.1 volts and sends it over to the CPU or GPU core and memory.
This isn’t as simple as it sounds and requires precision. Even one voltage spike can damage the processor, turning it into an expensive paperweight. The VRM consists of three parts: MOSFETs, chokes or inductors and capacitors. There’s also a controller chip that regulates the voltage, called the PWM controller.
The above is from a PowerColor Radeon RX 5700 XT Red Devil. The part highlighted by the white box is the GPU Core VRM and the two black boxes show the memory VRM. The red ones are the inductors (chokes), the green ones are the MOSFETs and the blue ones are capacitors. Every VRM will consist of these three components, regardless of the motherboard or graphics card. There are two more sets of VRMs, one below the core VRM and one to the left of the GPU. These are the SoC and VDDI (memory voltage controller) railings.
Multi-Phase VRMs and Doublers
Most modern GPUs and CPUs leverage multi-phase VRMs. These are more efficient and reliable than single-phase VRMs. They function by distributing the supplied power among themselves, reducing the load on the individual components as well as the heat produced.
The various phases of a VRM take turns to supply power to the CPU/GPU, each supplying a small portion of the required amount. This not only improves the heat dissipation and efficiency but also helps power processors with higher TDPs safely.
Only one phase is active at a time, but the amount of power supplied remains constant. The higher the phase count, the more power can be supplied safely, thereby reducing the stress and heat each phase handles.
VRMs are usually named as 6+1 or 8+2. This means that six or eight phases are for powering the CPU/GPU core and one or two are for the memory. In some cases, you’ll have motherboards with 12 phases or more. These are mostly just six-phase VRMs using doublers to essentially “double” the capacity.
VRM doublers work by distributing the power amongst the two lanes of MOSFETs, chokes and capacitors available to each of them. Usually, the PWM controller sees every two lanes controlled by a doubler as one. This allows PWN controllers with support for up to 6 phase VRMs to be used in 12 phase VRM designs using doublers.
While still better than regular six-phase parts, they’re not as efficient as, say eight or 10-phase VRMs. They induce a delay and reduce the frequency of the supplied current in half. Furthermore, only one of the two can be switched on at a time. The first one sees a modest delay but the second one is usually delayed by half a cycle, and in terms of precision, even the former is rather substantial.
While multi-phase VRMs kick in instantly, or one after the other without a notable delay in between, pseudo-phases using doublers induce a latency which reduces the overall efficiency.
Doublers are usually implemented to reduce costs and improve product value. Here’s an example:
Have a look at the back-side of the PCB. The red arrows are pointing to the doublers. There are five of them. Each splits (or balances) the power between the two phases they are connected to and allow the 4+1 phase PWM controller to be used as an 8+2 phase.
Again, a 5 phase VRM doubled to 10 is less efficient than a native 7 phase or eight-phase VRM. The reason as already explained is that the doublers induce a small delay to the PWM signals. Regardless, a 10 phase (doubled) VRM is still better than a 5 phase and is a cheap trick to allow a higher power draw.
VRM and Overclocking
A good quality VRM is essential for overclockers. It allows increasing the power consumption past 100% and at times a good VRM can also supply slightly more voltage than spec. A low-quality model will result in shutdowns and other anomalies upon overclocking.
Japanese capacitors are considered the best while Ferro-magnetic Alloy chokes tend to be more efficient than the rest. It’s also useful to get graphics cards that have a separate heatsink or cooling solution for the VRM as it tends to heat up.