Voltage regulation: the amount of voltage change between low and high loads. As loads increase, voltages will drop. The less they drop over the range of loads, the better a PSU is.
Ripple/noise Suppression: the quality of the DC power produced is dependent on the filtering in the PSU. Ripple is a remnant from the AC-DC conversion and fluctuations/waveform of the source AC that needs to be kept to a minimum to prevent damage to components that are plugged into the PSU. The lower the ripple, the better a PSU is.
Efficiency: percent of power not lost to heat when the AC power is converted to DC for use by the computer.
Nope, a decent 400-500W PSU can handle just about any single card setup (for example a g92 and a C2D or C2Q).
Built quality (component selection), performance (voltage regulation, ripple suppression, efficiency) and total amperage on the 12V rail all determine how good a PSU will be.
PSU performance can be limited by high operating temperatures. As temperatures increase the PSUâ€™s power output will drop, often called the de-rating curve. Poor main power (brown outs/surges) can also affect a PSUâ€™s performance and life span.
Multiple rails are not necessary but they do add another level of safety. They do no increase performance or stability since they are essentially the same as a single rail. The only difference between the two is that there is what is called an OCP (Over Current Protection) that limits the amount of power to each rail. There are occasions where there will be a short that does not trigger the short circuit protection, and those shorts can heat up a wire or connector and lead to a fire. The advantage a multi-rail PSU has is that these types of shorts will not be dangerous since the total amperage available to that wire or connector is limited to something like 18-20A for a usual setup. This can be seen as a real benefit when we start to use PSUs with 60+A available on the 12V rail.
It is quite dangerous to open a PSU since capacitors can hold charges for months. Another thing most people donâ€™t realize is that the heatsinks in a PSU are also live which really limits what you are allowed to touch safely.
When shopping for a PSU, OEM (most PSU companies donâ€™t actually make their own PSUs, they are contracted out to a manufacturer and then are rebranded by the reseller), build quality, performance, efficiency and 12V amperage are important things to look at. Well done reviews are the best place to start. Sites such as hardOCP.com and jonnyGURU.com currently have the most comprehensive reviews.
There is not much you can do to mod a PSU to make it better. Of course if you are handy with a soldering iron, you can replace caps and other important components with higher quality parts. But more often than not, it would be more expensive to buy a cheaper PSU plus extra parts than it would to just buy a better quality PSU in the first place.
The best PSUs Iâ€™ve seen so far would probably be the Antec Signatures. They have the best combination of voltage regulation, ripple suppression, efficiency and overall build quality of any PSUs Iâ€™ve seen tested so far.
Well, top 2 sub $100 would easily be the Corsair TX750 and the PC P&C Silencer 750. I donâ€™t really have a 3rd one I recommend often that is normally priced under $100.
<$75 would be Corsait tx650, Silencer 610 and Antec EA650
<$50 would be Corsair cx400, EA380, EA430 and EA500 depending what is on sale.
These are all sale prices which can be frequently had.
There is a point of having too high of capacity PSU. If you do not load a PSU to the 25-50% range you will not reach maximum efficiency. So with your example of a 1200W PSU, if it were paired with a system that would never use even 500W the majority of the time the computer is on it will not be in the efficiency â€œsweet spotâ€. The other side to this is that good components are not cheap. Often it is not feasible to sell a high quality 500W because of the cost of good components. But if you go up to say 750W, the cost of quality parts wouldnâ€™t be much more than for the 500W and now the company can make a profit and the consumer can buy a quality PSU for a reasonable price that would only be $10-20 more compared to the 500W. I didnâ€™t explain that well, hopefully it came across.
Total 12V amperage of PSU will be listed on the label. For example, it will say 4 rails at 18A max each and combined would be 60A. If the PSU does not label its total 12V amperage it usually means the manufacturer has something to hide and the PSU may not be very good.
Neither are more efficient since they are essentially the same design with a multi rail have an extra circuit for safety.
Green to ground (black) will start a PSU. Some PSUs are picky about with ground you use, but usually the one right beside the green wire works just fine.
I explained the modding thing earlier; itâ€™s feasible but not cost effective.
Efficiency of a PSU is determined by the topology of its switching transistors. There are many different variations with each design having its pros and cons. The different arrangements and their effects on efficiency are one of the things I am still learning
It is possible to discharge a cap using a resistor but it is something I have never done or have seen done. It is best to just not touch charged components and it is even better to avoid opening a PSU altogether.
A test done by jonnyGURU many years ago showed that a properly implemented modular design (i.e. no loose connections) has very little effect on voltages. Often times the voltage drop due to the extra resistance of the extra connection was no worse than what is seen over a foot or two of wire.
There shouldnâ€™t be much effect as far as I know.
There is sometimes a world of difference. Many cheapo PSUs cannot deliver their label wattage at any temperature. They are also prone to poor voltage regulation and efficiency when asked to do high loads. They normally have poorer quality components and a much higher failure rate compared to tested and respected PSUs.
There is no rating system. The ATX 12V standard has guidelines to be followed, like what rails there need to be and the maximum amount of voltage regulation and ripple allowable. But when it comes to voltage regulation and ripple suppression, there are no dedicated enforcement agencies for quality and honesty of their claims. There is no standard in terms of what temperatures PSUs are to be rated at or how to determine the wattage rating of a PSU. There are trends, but not standards. For example, lower quality PSUs will be rated at 25C while high quality PSUs are rated at 40-50C. Also, a modern PSU should have 90% or more of its capacity available on the 12V rail. Often what you see is companies trying to pass off older designs (less 12V and more emphasis on the 3.3/5V rails) and rating them with a higher total wattage than what they should be.
3.3V- ram and a small amount for video cards
5V- logic boards on the HDDs, floppy, optical drives, USB, maybe some use on the mobo
12V- GPU, CPU, HDD/optical drive motors, fans
For measuring ripple I will refer to the ATX12V Design Guide: http://www.formfactors.org/developer...20PSDG2.01.pdf
(PDF) section 3.2.6
The accuracy of the voltages is more important than a PSU being able to provide its rated capacity. The main voltages must be within 5% to be safe. So the 12V rail must stay between 11.4V-12.6V.
I remember a guy over at XS making his own linear PSU. It was a monster. It is very difficult and not feasible for anyone without an intimate knowledge of PSU design.
You can futureproof by buying 30-40% more PSU than you need. It would leave room for reasonable future upgrades while still stressing the PSU to the recommended level.
Peak efficiency is normally between 25-50%. But it can vary based on design.
Most mid range systems (C2D and 8800gt/4850) will be fine with 30-35A. A quad and a 4870 will start to need ~40A. Mid range SLI/Crossfire should have 45-50A. High end (C2Q and 2 4870/gtx260) should have no less than 60A especially if you are overclocking.
Yup, explained earlier. Higher temps= performs worse.
Normal operating temperatures for a PSU would be between 30-40C depending on room temperature. So if a PSU rated at 25C is used in a 35C environment, it may not be able to do its rated capacity. But if you have a 50C rated PSU, it will be able to perform to its rated capacity in almost any situation up to 50C which is very rare in a normal setting.
It is somewhat of a gimmick. But there is some logic behind it. When PSUs start getting into the 1000+W range they will need to dissipate 200+W of heat. That can be difficult for a air cooled PSU which is where the water cooling comes in. Is water cooling necessary? No. But it isnâ€™t necessary to water cool CPUs either but we still do
There is no standard way to calculate total wattage. Each company can do as it pleases. I explained the trends in a previous question.
kW PSUs are good for the epeen? Nothing necessarily bad about overkill, the large PSU will just have a lower efficiency than a better matched PSU.
PSU are rated based on what they are able to produce in DC, not the amount of AC they draw from the outlet. The difference between the two is a PSUâ€™s efficiency.
Explained earlier: build quality, performance, safety features and lifespan are what differentiate a good PSU from a bad one.
Wrote up quickly, probably some errors. And as always, the stickies here explain things better than I can: