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Mike Farabow
Mike Farabow

How To Buy A Psu

Generally, more complex systems require more power to run. A desktop with a custom liquid cooling loop, a high-end motherboard, and dual GPUs is going to need a higher wattage computer power supply than a simpler system.

how to buy a psu

Consider EfficiencyWattage is certainly an important consideration when choosing a desktop power supply, but so is PSU efficiency. Inefficient delivery leads to wasted power and more heat, which can potentially decrease the lifespan of your components.

A lot of no-name PSU manufacturers list their power supplies at wattage ratings that are much higher than what they can actually deliver over a given period of time. Some first-time PC builders make the mistake of thinking that just because a power supply has a high wattage rating, that means it is a good enough power supply for their needs.

And, because a lot of these low-quality power supplies come in at ridiculously low prices, some make the mistake of thinking they are getting a solid power supply for a great price. The reality, though, is that they are purchasing a very bad unit that has a misleading wattage rating.

During this conversion, there is some loss of power to heat. So, 100% of the AC power drawn from the wall does not get converted into DC power. A decent power supply will convert at least 80% of the AC power it draws from the wall into DC power.

In order to earn one of the 80 Plus badges, a power supply must maintain a specific level of efficiency when it is under 20%, 50%, and 100% load. (The newest 80 Plus rating, Titanium, considers a power supplies efficiency when it is under 10% load.)

You can spend a lot of time ensuring that your other components are color-coordinated and you can have the cleanest cable management around and you can show it all off inside of a case with a nice full-glass side panel.

Hi, just a thank you for the comprehensive yet concise article with technical content made accessible through well structured writing that lead me from ignorance to enlightenment (regarding my PSU hunt at least) in seconds, and wider kudos for the site as a whole. Such a rarity to find quality content, especially without pop ups, affiliate links and sponsored content.

Some power supply manufacturers will build in protections to help keep your components safe from power-related issues. These protections often add some cost to a power supply, but they can offer some additional peace of mind as well.

The first is overvoltage protection, which refers to a circuit or mechanism that shuts down the power supply unit if the output voltage exceeds the specified voltage limit, which is often higher than the rated output voltage. This protection is important since high output voltages may cause damage to computer components that connect to the power supply.

The second is overload and overcurrent protection. These are circuits that protect the power supply unit and the computer by shutting down the power supply unit when there is excessive current or power load detected, including short circuit currents.

Although there are still AT form factor power supplies available for purchase, AT form factor power supplies are undoubtedly legacy products, on the way out. Even the later ATX form factor power supplies (ATX 2.03 and earlier versions) are falling out of favor. The major differences between the ATX and AT power supply form factors are:

The ATX12V form factor is the mainstream choice now. There are several different versions of the ATX12V form factor, and they can be very different from one another. The ATX12V v1.0 specification added over the original ATX form factor a 4-pin +12V connector to deliver power exclusively to the processor, and a 6-pin auxiliary power connector providing the +3.3V and +5V voltages. The ensuing ATX12V v1.3 specification added on top the 15-pin SATA power connector on top of all that.

A substantial change occurred in the ATX12V v2.0 specification, which changed the main power connector from a 20-pin to a 24-pin format, removing the 6-pin auxiliary power connector. Also, the ATX12V v2.0 specification also isolated the current limit on the 4-pin processor power connector for the 12V2 rail (+12V current is split into the 12V1 and 12V2 rails). Later, the ATX12V v2.1 and v2.2 specifications also increased efficiency requirements and mandated various other improvements.

The Small Form Factor (SFF) designation is used to describe a number of smaller power supplies, such as the SFX12V (SFX stands for Small Form Factor), CFX12V (CFX stands for Compact Form Factor), LFX12V (LFX stands for Low Profile Form Factor) and TFX12V (TFX stands for Thin Form Factor). They are all smaller than the standard ATX12V form factor power supply in terms of physical size, and small form factor power supplies need to be installed in corresponding small form factor computer cases.

Next up is the processor power connector, which comes in 4-pin and 8-pin versions. As with the main power connector, many modern motherboards have switched to the larger format. Again, make sure your power supply is compatible.

The power supply is the beating heart of your gaming PC, the part that circulates the vital life-blood of power around your expensive processor, motherboard, and graphics card. The power supply can dictate the limits of your ambitions when it comes to potential PC upgrades, so it's always worth keeping one eye on the future when it comes to picking your next power supply.

You have to determine first how many Watts your system, or prospective system consumes, and on top of that, you have to leave enough headroom for future upgrades. Moreover, you should keep in mind that the sweet efficiency spot is usually around 40-50% of the PSU's max-rated capacity. That and the closest a given power supply is to its max load output, the lowest the efficiency.

So, if your system needs 500W at full load, it's not wise to get a 550W PSU but, at least, a 650W one. That said, most of us won't highly stress our systems all-around the clock unless you somehow have the time to constantly play games. Gaming can be seriously taxing on your PSU since they will generally fully load your graphics card, which is likely the most thirsty part of your setup.

To get an idea of what your system, or dream upgrade, will look like in terms of power draw you can easily enter all the particulars into a handy PSU calculator. We like to use the OuterVision Power Supply Calculator (opens in new tab), but there are others available.

The most accurate way to determine your system's power needs is to use a kill-a-watt device and take some readings under full load, that's useful if you want to replace the existing PSU. Note that this procedure will only give you an indicative reading since it doesn't take into account your PSU's efficiency.

The most energy-demanding parts in today's systems are the GPUs with the CPUs following. Unfortunately, the manufacturers do not provide clear information on the actual GPU power consumption, and to make matters worse, you also have to consider possible power spikes that can reboot the system if the PSU isn't strong enough to handle them.

On top of that, Intel and AMD's official TDP values for their CPUs are not even close to the actual power consumption numbers since they refer to normal and not boost clocks. Under increased frequencies, CPUs draw much more Watts than the official TDP from the PSU, and things get even worse, of course, if you decide to overclock.

Even at default settings, some high-end CPUs can ask for 300W or more power. Yes, we're looking at you Mr. Core i9 11900K. If you combine this with a high-end GPU's power consumption, you will quickly figure that you need an 850W or even stronger PSU for a high-end gaming system.

The PSU's dimensions play a role in your next system build. You cannot use a standard ATX12V power supply in a mini-ITX chassis which requires an SFX PSU, for example. Thankfully, the prevalent desktop PSU form factors are restricted to the following

The SFX-L is not an official ATX spec format, since it was introduced by Silverstone in 2014 and several other brands subsequently adopted it. It has longer depth than SFX to allow for a stronger platform.

You've probably heard of Titanium, Platinum, Gold, and other metal ratings in PSUs. These indicate the PSU's efficiency, in other words, how much power the PSU draws from the socket to deliver power to your system. The more efficient the power supply, the better for the environment since it minimizes your carbon footprint. On top of that, you also save money on electricity in the long run.

Another significant decision you have to make before you invest in a new PSU is what type of cables do you go for; modular or not? Usually, the higher-end power supplies, which cost more, come with fully modular cables. You will generally only find fixed cables in the budget categories, and somewhere between the middle, you will discover semi-modular PSUs. Many of those also belong to the budget or mid-tier categories.

If you can deal with fixed cables and need a PSU for a mainstream system, there is no need to pay more for a fully modular unit. But if you're aiming to use the bare minimum cabling, without a huge number of wires floating around your system, then a full or semi-modular setup is the way to go.

More and more people are starting to realise what an impact the PSU has on a system's overall noise output. As weird as it might sound, your power supply can play a significant role in the noise of your PC under load.

The higher the efficiency, the lower the thermal load, so the PSU's fan doesn't have to spin at high speeds. This means that your best bet for a silent PSU is to buy one with the highest possible efficiency rating. Still, this doesn't mean you will select a dead quiet power supply, so it is good to read some reviews before continuing with the purchase.

We've noted our own tested noise ratings in our best power supply (opens in new tab) guide to give you an idea of how the top PSUs sound. Cybenetics offers PSU noise certifications, so with a quick look in the corresponding database, you will find the PSU that meets your acoustic demands. 041b061a72




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