5 Things to Pay Attention to When Choosing A Power Supply

By MSI |
With the introduction of NVIDIA GeForce RTX 30 series graphics cards, AMD Ryzen 5000 series processors, and Radeon RX 6000 series graphics cards, the era of high performance is here, signaling a gradual increase in the demand for higher-performing power supplies.

There are many power supply options out there in the market. How should players choose a power supply that best suits their needs in this wave of PC upgrades? Several areas should be paid attention to when purchasing a power supply:

Power Wattage

Before discussing the specifications of other power supplies, the most basic concept of the power supply wattage needs to be explained first. The wattage indicated on the power supply may be different from what the actual wattage is. A good power supply will indicate the continuous rated power while other power supplies may only indicate the peak output power, which means they cannot provide sufficient power. The specification sticker on each power supply and the specification table marked on the packaging can help with judging the authenticity of a power supply. The following is a more in-depth explanation of continuous rated output power and peak output power:

Continuous Rated Power

This is the maximum power value within the range of the power supply that the power supply can continuously provide under any input voltage and temperature. Generally, the specification sticker on the back of the power supply is subject to safety regulations, so it must indicate the total rated output power that the power supply can provide, that is, the wattage that the power supply can provide.
power

Peak Output Power

This is the peak output power value that the power supply can provide in a short time (T <10mS) before triggering the protection mechanism. Generally, the peak output power of a power supply is designed to be 1.1 times the rated power, and most power labels and specifications do not indicate the peak output power. For an 850W power supply, its instantaneous maximum output power is about 935W (850W x 1.1 = 935W).
For some power supplies, you will find that the total rated output power indicated on the specification sticker is not the same as the wattage on the product name or description. So when buying a power supply, look at the indicated total rated output power and make sure you're getting the right amount of wattage.

Safety Protection

Another key indicator in choosing a power supply is to understand what protection functions the power supply has to ensure that the power supply will be protected during times of abnormal activities. The general protections are OVP/OCP/OPP/OTP/SCP. A brief description is given below;

OVP (Over Voltage Protection)

When the power supply is acting out, the output voltage will rise abnormally. If the voltage exceeds the voltage defined by the specification, the power supply output voltage will be cut off in time. The power supply can be restarted after the abnormality is eliminated. Therefore preventing damage to the components or the motherboard.
Definition Provided by Intel's Design Guide:
power

OCP (Over Current Protection)

When the current provided by each rail of voltage exceeds the maximum output current tolerated by the power supply, the power supply will be cut off in time for protection. After the abnormality is eliminated, the power supply can be restarted.

OPP (Over Power Protection)

If the power consumption of the system exceeds the rated power of the power supply, and the power supply will be cut off in time for protection.

OTP (Over Temperature Protection)

When the internal temperature of the power supply exceeds the design tolerance (due to poor heat dissipation or abnormal fan), the power supply will be cut off in time for protection. When the internal temperature is back to normal, it can be restarted.

SCP (Short Circuit Protection)

When the output circuits are short-circuited, the power supply will be cut off in time for protection. After the abnormality is eliminated, the power supply can be restarted.

Power Supply Rail Design and Wattage Requirements

The rail design of the power supply is distinguished into single-rail and multi-rail. Each design has its advantages and application methods. The difference between the so-called multi-rail and single-rail design is that a power supply has several +12V power outlets. +12V is the core system power source, so the current required is relatively large. CPU, GPU, MB are all provided by +12V current. Generally, whether the power supply is single-rail or multi-rail can be judged from the specification table.

Single-Rail Design

As the name implies, there is only one +12V channel, and all current will be provided to the system components through this channel. The advantage of a single-rail is that all the available current is concentrated in the same circuit under the total power supply, so the amperage of a single circuit that can be supplied is relatively large. Only one +12V is displayed on the specification sheet and it indicates the maximum amperage and wattage that can be used.
power

Multi-Rail Design

The multi-rail design splits +12V into multiple channels. This limits the amperage of each channel and installs an OCP protection device on each channel to ensure that each channel will not be damaged due to excessive current load, which improves user safety. The specification sheet will be split into multiple rails of +12V and indicate the maximum amperage and wattage that can be used for each. However, no matter how many channels there are, the total wattage remains the same. Take MPG A850GF as an example, it is split into 4 channels to supply power to MB, CPU, and VGA respectively, and the total wattage provided is 850W.
power
Different circuit design and protection mechanism settings will affect the maximum wattage that the power supply can withstand, corresponding to the peak output power. Generally, power supplies' peak power will be designed to be 1.1 times the rated power before the protection mechanism is activated. After the protection mechanism is activated, it depends on the OCP and OPP protection values set by each company. OCP is usually more influential in the multi-rail design and for single-rail OCP settings are almost the same as OPP settings.

The MSI MPG series power supply adopts a 4-channel multi-rail design, and the OCP value of each channel is set to 1.35 times the average value of the rated power. Take MPG A850GF as an example. Each +12V channel is based on the highest ampere marked. The number multiplied by the OCP setting value represents the highest instantaneous power it can withstand, usually depending on the CPU and VGA settings. Different installation methods will also determine how much wattage the VGA and CPU can get. It is recommended that VGA be plugged into VGA1 and VGA2. Do not install on the same channel so that VGA can get a larger current supply under the safety protection mechanism. Refer to the official website for the recommended installation method.

OCP Converted Power Calculation Value

+12VCPU: 25A x 1.35 x 12V = 405W
+12VVGA1: 40A x 1.35 x 12V = 648W
+12VVGA2: 40A x 1.35 x 12V = 648W

OPP is set at an average value of 1.35 times the rated power, so the entire power supply can reach 1147W (850W x 1.35 = 1147W) instantly.

We used the game benchmark to simulate the power consumption required by players when playing games on 4K and FHD resolution settings. We also used the AIDA64 + 3Dmark D12X test to check how much wattage is required to meet the demand under the most wearing conditions.

The following is the list of components used in the test samples:

Test Sample 1
  • MB: MEG Z490 ACE
  • CPU: Intel i9-10900K (Turbo Boost on)
  • VGA: RTX 3090 Gaming X Trio
  • PSU: MPG A850GF
Test Sample 2
  • MB: MEG X570 UNIFY
  • CPU: AMD Ryzen™ 9 5950X (Game Boost on)
  • VGA: RTX 3090 Gaming X Trio
  • PSU: MPG A850GF
power
power




From the conclusion we can draw from the game simulation and stress tests, we can see the average wattage (RMS wattage) doesn’t exceed 600W, and for peak wattage (Max wattage) the wattage is all within the protection range of OPP (MPG A850GF is 850W x 1.35 = 1147W). Although the official suggestion from NVIDIA is to pair RTX 3090 with a 750W power supply, but the tests indicate that a 850W power supply is more sufficient.

Modular Cable Design & Customization

The cable design of the power supply has three types: full modular design, semi-module design, and non-modular design. The main difference lies in whether the cables can be removed. The advantage of the full modular design is that the wires can be installed according to the assembly requirements to save space and improve cable management. The cables can also be customized. Most high-end power supplies currently on the market utilize a full modular design.
power
Also because of the fully modularized design such as the MSI MPG Series power supply's cables, players can customize the cables according to their preferences. Each power supply manufacturer has its design, so just understand the cable port's design and you can easily create customized cables.


power
MSI MPG series power supply power pin definition.


80 PLUS Power Efficiency Rating

The 80 Plus is a certification for the energy efficiency conversion of a power supply. It is divided into 6 tiers. The higher the level means higher the energy efficiency conversion rate and more power saving. Typically, to achieve a good conversion, the power supply needs to use better materials. The following are the conversion efficiency requirements of the 80 Plus energy consumption specification at different levels.
 msi power level


Currently, most of the high-end power supplies on the market are Gold tier, with higher wattage power supplies at the platinum and titanium levels. When buying, players can start with Gold tier full modular power supplies. Although the Platinum and Titanium tier power supply's power conversion efficiency and quality are better, the price is relatively high. The Gold tier power supply has relatively good conversion efficiency and the price meets the needs of general PC builds.
The MSI MPG A850GF / MPG A750GF / MPG A650GF power supply is an 80 Plus Gold full modular power supply. The multi-rail design improves the safety of the power supply. Choose a power supply according to the needs of your build and use. The chart below is how we recommend the NVIDIA GeForce RTX 30 series graphics cards and Intel/AMD CPUs to be paired with MSI's power supply products. The upcoming AMD card's power consumption numbers will be provided later on.
power
For more information, please refer to MSI’s website.
MPG A850GF https://www.msi.com/Power-Supply/MPG-A850GF
MPG A750GF https://www.msi.com/Power-Supply/MPG-A750GF
MPG A650GF https://www.msi.com/Power-Supply/MPG-A650GF
Subscribe to Our Blog

Stay up to date with the latest hardware,tips and news

By clicking the button, you agree to MSI's Terms of Service and Privacy Policy