VRM phases for Ryzen CPUs: how many are enough?

As experience shows, VRM manufacturers cannot do without multi-phase designs. Increasing the number of phases increases total current and power delivery and helps stabilize voltage. The purpose of power phases is to convert the input voltage into exactly the level required for the processor to operate.

This article explains how many power phases are required for the Ryzen 5600X, 5800X3D, and 5900X processors. In most cases, the number of phases specified by manufacturers is mostly marketing. Phases are labeled A + B, where A refers to the CPU core power phases and B to integrated graphics and memory. The “×2” symbol indicates the use of doublers…

General understanding of Power Phases

The VRM power delivery system is a system of components on the motherboard. It converts the high voltage from the power supply unit (usually 12 V) into a lower voltage required by the processor (around 1–1.5 V). The CPU also requires a high current draw, which can reach tens of amperes.

It includes the PWM controller itself, MOSFETs, inductors, and capacitors. The PWM controller determines how much power needs to be delivered to the CPU. The other components perform regulation and signal filtering functions. The wider the pulses are, the higher the current supplied…

Each power phase delivers power to the processor. It is a circuit made up of capacitors, inductors, and transistors that must operate in synchrony. The more true power phases there are, the more stable and cleaner the output voltage will be.

How much power do Ryzen CPUs consume?

The thermal design power (TDP) of the Ryzen 9 5950X is rated at 105 W, but its power limit is set to 142W. In practice, when boosting up to 4.6 GHz, power consumption rises to 231 W. Under a heavy Cinebench R23 load, the current draw reaches 163 A at a voltage of 1.42 V.

All processors have already been extensively tested. You can find power consumption data for any of them. This value may vary depending on load, frequency, and voltage settings. It is important to note that overclocking and stress testing are indeed extreme operating conditions…

VRM real-world performance and limits

For example, the GIGABYTE X570S AORUS MASTER motherboard features an updated VRM design. It has a 14+2 phase power delivery design, and the XDPE132G5C PWM controller can control all 16 phases. It is equipped with Infineon TDA21472 MOSFETs, rated at up to 70 A.

In the technical specifications of this MOSFET, we need to examine the operating characteristics. We are interested in the current vs. temperature graph (Fig. 5). The rated 70 A can only be achieved at sub-zero temperatures. At 60 °C, it provides approximately 50 A, which gives 14 phases × 50 A = 700 A.

The efficiency graph (Fig. 4) shows that at a current of 50 — 55 A, efficiency is about 92%. Theoretically, this configuration corresponds to 700 A × 92% = 644 A to the CPU. In practice, temperatures are higher, meaning the maximum possible load is even lower. These are real phases without doublers…

How many power Phases are required for Ryzen 5000?

For 12- and 16-core CPUs (200+ W), 6 phases (minimum 40 A) with doublers are required. 8-core CPUs (up to 150 W) require 5 phases (minimum 50 A) with a doubler or DualOut configuration. 6-core CPUs (75 W) require at least 4 actual phases. Please refer to the table, as 6 power phases using 50 A and 90 A MOSFETs are not the same thing.

Table 1. X570 and X570S motherboard VRM ratings

It indicates how many phases are required for Ryzen CPUs, taking VRM capabilities into account. In practice, a 6-phase power delivery system is more than enough. Such setups typically feature high-quality VRM cooling. A 6 × 2 configuration (50A with doublers) allows the Ryzen 9 5950X to be overclocked comfortably.

Table 2. B550 motherboard VRM ratings

Following the X570 chipset, the new B550 was introduced, which also performed very well. Some models feature equally high-quality power delivery systems. For example, the GIGABYTE B550 AORUS MASTER motherboard is even better than some X570 boards, and its VRM section is comparable to the X570S model. In this case as well, 6 — 7 phases are more than sufficient.

It is still too early to write off X470, B450, and even X370 motherboards. In our previously linked table, previous-generation models are listed, such as the ASUS ROG Crosshair VII Hero and the ASRock X470 Taichi, which are still relevant. Take a look at the AM5 platform as well — a VRM table for AM5 motherboards for the Ryzen 9600X, 9700X, 9950X, and others.

Conclusions

Marketing hype. For example, the VRM temperature of the Gigabyte X570 AORUS Extreme motherboard is 49 °C under a 125 W load. Meanwhile, the MSI MPG X570 GAMING EDGE WIFI reaches 96 °C. At 165 W, it goes up to around 130 °C, using a Ryzen 9 3900X at 4.2 GHz and 1.4 V, resulting in throttling. So much for how many power phases Ryzen actually needs…

More power phases result in a more stable CPU voltage. Total current increases through actual phases, doublers, or parallel MOSFET configurations. At the very least, good VRM cooling reduces power losses. Component quality is also important.