Voltage regulator module

A voltage regulator module (VRM), sometimes called processor power module (PPM), is a buck converter that provides a microprocessor the appropriate supply voltage, converting +5 V or +12 V to a much lower voltage required by the CPU, allowing processors with different supply voltage to be mounted on the same motherboard.

Some voltage regulator modules are soldered onto the motherboard, while others are installed in an open slot designed especially to accept modular voltage regulators. Some processors, such as Intel Haswell CPUs, feature voltage regulation components on the same package (or die) as the CPU, instead of having a VRM as part of the motherboard; such a design brings certain levels of simplification to complex voltage regulation involving numerous CPU supply voltages and dynamic powering up and down of various areas of a CPU. A voltage regulator integrated on-package or on-die is usually referred to as fully integrated voltage regulator (FIVR) or integrated voltage regulator (IVR).

Most modern CPUs require less than 1.5 V, as CPU designers tend to use smaller CPU core voltages; lower voltages help in reducing CPU power dissipation, which is often specified through thermal design power (TDP) that serves as the nominal value for designing CPU cooling systems.

Some voltage regulators provide a fixed supply voltage to the processor, but most of them sense the required supply voltage from the processor, essentially acting as a continuously-variable adjustable regulator. In particular, VRMs that are soldered to the motherboard are supposed to do the sensing, according to the Intel specification.

Modern graphics processing units (GPU) also use a VRM due to higher power and current requirements. These VRMs may generate a significant amount of heat and require heat sinks separate from the GPU.

The correct supply voltage is communicated by the microprocessor to the VRM at startup via a number of bits called VID (voltage identification). In particular, the VRM initially provides a standard supply voltage to the VID logic, which is the part of the processor whose only aim is to then send the VID to the VRM. When the VRM has received the VID identifying the required supply voltage, it starts acting as a voltage regulator, providing the required constant voltage supply to the processor.

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