Voltage regulator module
Encyclopedia
A voltage regulator module or VRM, sometimes called PPM (processor power module), 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. Some are soldered to the motherboard
while others are installed in an open slot. It allows processors with different supply voltage to be mounted on the same motherboard. Most modern CPUs require less than 1.5 volts. CPU design
ers tend to design to smaller CPU core voltage
s; lower voltages help reduce CPU power dissipation
, often referred to as TDP or Thermal Design Power
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 resistor
. In particular, VRMs that are soldered to the motherboard are supposed to do the sensing, according to the Intel specification.
The correct supply voltage is communicated by the microprocessor to the VRM at startup via a number of bits called VID (voltage identificator). 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.
Modern GPUs also use VRM due to a need of more power and high current.
Buck converter
A buck converter is a step-down DC to DC converter. Its design is similar to the step-up boost converter, and like the boost converter it is a switched-mode power supply that uses two switches , an inductor and a capacitor....
that provides a microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
the appropriate supply voltage, converting +5 V or +12 V to a much lower voltage required by the CPU. Some are soldered to the motherboard
Motherboard
In personal computers, a motherboard is the central printed circuit board in many modern computers and holds many of the crucial components of the system, providing connectors for other peripherals. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple...
while others are installed in an open slot. It allows processors with different supply voltage to be mounted on the same motherboard. Most modern CPUs require less than 1.5 volts. CPU design
CPU design
CPU design is the design engineering task of creating a central processing unit , a component of computer hardware. It is a subfield of electronics engineering and computer engineering.- Overview :CPU design focuses on these areas:...
ers tend to design to smaller CPU core voltage
CPU core voltage
The CPU core voltage is the power supply voltage supplied to the CPU , GPU, or other device containing a processing core...
s; lower voltages help reduce CPU power dissipation
CPU power dissipation
Central processing unit power dissipation or CPU power dissipation is the process in which central processing units consume electrical energy, and dissipate this energy both by the action of the switching devices contained in the CPU and by the energy lost in the form of heat due to the impedance...
, often referred to as TDP or Thermal Design Power
Thermal Design Power
The thermal design power , sometimes called thermal design point, refers to the maximum amount of power the cooling system in a computer is required to dissipate. For example, a laptop's CPU cooling system may be designed for a 20 watt TDP, which means that it can dissipate up to 20 watts of heat...
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 resistor
Resistor
A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...
. In particular, VRMs that are soldered to the motherboard are supposed to do the sensing, according to the Intel specification.
The correct supply voltage is communicated by the microprocessor to the VRM at startup via a number of bits called VID (voltage identificator). 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
Voltage regulator
A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. A voltage regulator may be a simple "feed-forward" design or may include negative feedback control loops. It may use an electromechanical mechanism, or electronic components...
, providing the required constant voltage supply to the processor.
Modern GPUs also use VRM due to a need of more power and high current.