Power Supply Units - Simplified

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Active member
Nov 2, 2006
Power Supply Units - Simplified


There is plenty of info on this forum about power supplies - I decided to round it all up.


The Myths:

1: Dual Rail +12v

Many of the PSUs distributed today comply with Intel's ATX 2.2 spec. This spec specifies that when the +12v rail exceeds 20A of power, a second rail must be added. There are some advantages to this (stopping >20A of power surging down a wire during a short), but it also has too many disadvantages for it to seem a logical decision on Intel's side. There is a very detailed thread about this, you can read through it here: >>PSU's---2 x 12v---The Dual Rail Myth<< Dual-rail PSUs aren't terrible, but they aren't as powerful as their single-rail counterparts.

2: Modular Plugs

PSUs with modular plugs are no good. When you're supplying current to something you want as little gaps in the voltage transition as possible. Modular plugs reduce efficiency and power. They may be good for cable management, but for strong stable power, they aren't the way to go.

3: SLI Certified PSUs

PSUs with the SLI certification are not guaranteed to run a high-end system. Nor one with high-end single/dual graphics. Thinking a PSU is a great one because of the sticker on the box isn't the way to go.

4: Q-Tec PSUs

Q-Tec are the worst PSU manufacturer that exists to date. Their PSUs may cost next to nothing, but they are worse than the no-name PSUs that are totally overrated. AVOID THESE PSUs AT ALL COSTS!!

5: Coolermaster PSUs not powering up some MSI mainboards

Our knowledge of this is that it's Coolermaster's problem. It appears some/most of the "Real Power" series refuse to boot-up/POST with MSI mainboards. All you can do is use another PSU or mainboard. There is NO fix for this.

What are Your Current PSU Specs?

Telling us you have a '500w PSU' actually tells us very little. When describing your PC hardware, you should also list your PSU specs too. Look inside your PC and on the side of your PSU you should see a printed label:

Two examples:

List the brand, the output in watts, and the amp ratings on the 12v, 5v and 3.3v rails. Saying you have a 420w PSU is irrelevant, as there are better quality 360w PSUs, than some cheaper 550w models. We want to see: "My PSU is a Codegen 350w (3.3v/20a, 5v/30a, 12v/12a)", not "My PSU is 500w". If you provide this information, you will get better and faster advice. Just supplying a make and model name and expecting users to search the internet to find your PSU specs is just a wee bit rude, as they are already giving up their time to help you!

Why A Quality PSU:

Long life
Delivers specified power
Good warranty service

These 3 requirements are most important when choosing a PSU. Make sure every PSU you buy reaches these 3 requirements. If not think of the sparks, smoke and dying components again.


Why An Expensive PSU?

An expensive Powersupply not only gives you stable power and better problem protection.

But you also earn them back in a few years, as they use less energy to produce the same. They don't consume the watts that they are labeled, but they produce the power your system is asking.

However, more expensive PSUs have a better transformation then generic ones. Generic PSU's typical do 60~70% conversion of input -> output. More expensive ones do 80~90% conversion, exception is Q-Tec those do -100%.

So you are not only saving energy, your electrical bill will be a lot lower, this lower consumption will payback the extra costs mostly in about 4 years time.
As these PSUs typical last 10 years or more in the same system, just imagine how much money you didn't spend on your machine.

To be very short: Expensive PSUs save you money!

Which PSU is Best for Me?

Have a look at this topic: >>Choosing the Right Power Supply<<

Symptoms of A Bad/Dying PSU:

When a PSU comes close to the end of it's life (generic PSUs tend to live the shortest, Q-Tec PSUs live shorter), they can cause a computer to do some pretty crazy things. Common symptoms are:

Random shutdowns
Failing to cold boot
Shutting down under load
Making weird noises

If a PSU fails while the computer is running, this can be fatal for some of your components. I've lost CPUs, mainboards, memory and VGA cards to dying PSUs on their final breaths. Sparks and smoke... It isn't pretty. Surprise, surprise, this was all with generic PSUs.

>>Is your problem caused by your PSU?<<

The simplest check is to swap your current PSU for a quality one with plenty of amps on the +12v rail(s). Look above for symptoms of a bad/dying PSU.

Highly Recommended Manufactures:

1: Corsair (Top recommendation)

2: Seasonic

3: Silverstone

Recommended Manufactures that Make Single-rail PSUs:

Cooler Master (Silent Pro, GX or B series)

Super Flower
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