Power Supply Discussion thread

[GoodGame]

WARNING: NEVER OPEN A POWER SUPPLY: THEY ARE HIGH VOLTAGE, and can cause SERIOUS INJURY (DEATH?).


Just a thread for discussing power supply theory, how to pick one etc..



1. Modular vs. non-Modular

A modular power supply allows for easier cable management when assembling a system. Basically some of the power cables outputs of the PSU can be removed if you don't need them, making the interior organization of cables less messy.

2. Power consumption. (from tiger-direct)

Component Wattage Required
Motherboard 15-30
Low-end CPU 20-50
Midrange to high-end CPU 40-100
RAM RAM 7 per 128MB
PCI add-in card 5
Low to midrange graphics board 20-60

High-End graphics board 60-100
IDE hard drive 10-30
Optical drives 10-25

a. Tally up your system versus a chart to get an idea of the power demands.

b. But note that actually efficiency might resemble a bell-shaped curve. Peak efficiency is about 1/2 the rated wattage of your PSU, with it decreasing to the tails of the curve as your system over or under use the PSU.

 

[Genocidicbunny]

Hah, high-end graphics card 60-100W. Lets try 200-300W. Similarly, high-end CPU's can push 125W, and thats when they're on stock. If you mod the voltage, all bets are off.

For picking a PSU -- I wouldnt base my decision solely on modular vs nonmodular. Id much rather have a lower wattage quality PSU thats also nonmodular vs a higher wattage, crappy modular PSU. Aesthetics don't matter when a failure in the PSU can fry the rest of your system.

 

[Zelig]

The RAM figure is also off.

Adding up wattage for individual components isn't really worth the effort, hell: you can probably skip looking at wattage at all, just look at the brand and the +12V requirement for whatever GPU you're running.

 

[GoodGame]

Zelig,

What should the RAM figure be? Something to do with generational differences of the different DDRs?

I understand that wattage varies widely with brand, but is it really useful to not consider your specific build's requirements? What would you replace it with---standard watts per form factor? (e.g. 1000W for ATX, 550W for mATX, 300W for SFF)?

 

[Zelig]

Zelig,

What should the RAM figure be? Something to do with generational differences of the different DDRs?

I understand that wattage varies widely with brand, but is it really useful to not consider your specific build's requirements? What would you replace it with---standard watts per form factor? (e.g. 1000W for ATX, 550W for mATX, 300W for SFF)?

RAM figures are per stick, not per MB, newer versions of DDR do take more, but anything other than CPU and GPU doesn't really matter.

The vast majority of the time, unless you're trying to run real close to a particularly PSU's limit, you can pick out an appropriate power supply just based on what GPU you plan on using.

 

[GoodGame]

On finding the better make of PSU, I'm aware that many units are simply relabeled from other sources. Is there an efficient way to shop for the best sources despite relabeling, and without actually having the PSU in hand to check it's code #?

E.g.
Figure 3: Thermaltake Toughpower 750 W is manufactured by CWT.

http://www.hardwaresecrets.com/article/How-to-Discover-Your-Power-Supply-Real-Manufacturer/370/2

The current "master list" for the article is here: http://www.jonnyguru.com/modules.php?name=NDArticles&op=Story&ndar_id=24

 

[Fëanor]

Good reviews usually dig that info up. Of course good reviewers also test the PSU thoroughly and will judge it on the base of its performance rather than its maker's reputation.

 

[Tarkhan]

Newegg has a tool for quick and dirty wattage calculations. They don't ship to me but I can still use their site XD It's not completely accurate, but it takes into account the big consumers (GPU,CPU, RAM and Motherboard).

http://c1.neweggimages.com/BizIntel...ons.newegg.com/productfinders/powersupply.jpg

 

[Fëanor]

It adds 30+ W for each additional 5400RPM HDD you got, that's utterly moronic. Even during the power hungry Spin-up rarely drain over 10-15 W.

 

[cardgame]

maybe they want you to buy more expensive PSUs

 

[Tarkhan]

Yeah, thats why I say not completely accurate

It can tell you if you should get a 550w or a 700w though.

 

[GoodGame]

More fuel for the fire:

http://www.wikihow.com/Buy-a-Power-Supply


1. The Wattage of a PSU may vary with the voltage connection; pay extra attention to the 12volt rating. And the Wattage rating for the 12 volt may be exaggerated/confounded based on the max efficiency understanding that a PSU operates best at a voltage 1/2 it's rating. In other words some manufacturers sell "600W" PSUs that are actually "300W" since the convention is a builder of a 300W system would buy a 600W for the efficiency. In other words, beware mislabeling.

A PSU's wattage rating isn't conducive to determining amperage at any specific voltage. All PSUs will have a sticker with their rated amperage at each voltage level. This information should be provided when purchasing a PSU from an online vendor and visible on the unit's retail box. As mentioned above, modern computers are 12V-heavy loads. A 500W PSU may sound adequate, but if its 12V amperage is in the low 20s or less (12V times 25A is 300W), it may not be able to power a modern computer.
....

To ensure reliable performance, 3D graphics-card makers recommended oversized power supplies. For example, a 600W supply to ensure 300W of +12V. Cost-conscious manufacturers, in turn, produced power supplies labeled "600W" that could produce 300W of +12V, but not more than that, knowing their customers would never actually ask for more power. Modern power supplies are all "12V heavy" in this way, able to produce most of their total output in the form of 12V, but overoptimistic manufacturer ratings are still common among cheaper power supplies

2. Modular is a desireable feature to create better cooling wind tunnels within your case.

Get a modular PSU. It will help eliminate extra wires to get in the way of cooling. Ignore the claims by PC Power & Cooling that modular cables create more resistance due to corrosion of contacts. The additional resistance is negligible.

3. Top quality brands:

Top Quality (based upon electrical capabilities): PC Power & Cooling, Seasonic, Zippy, Silverstone, Enermax, Antec, Acbel, Akasa, AMS, Channel Well, Corsair, Etasis, FSP, OCZ, Thermaltake, Zalman.

Stick with a top quality brand unless you're building a very low end system that will be running at stock (i.e. all low end components); then even a notorious Rosewill PSU is acceptable to keep costs down.

 

[tokala]

This is a nice article covering the "How big a PSU do I need" question by a guy who is testing PSUs for a living.
The tl;dr; version: For 90% of all systems, a 300W PSU would be sufficient, for >95% a 400W PSU. This of course refers to quality brands like the ones mentioned by GoodGame.

This article is a few years old, but still very relevant, as most components today consume rather less power. More or less only the most expensive video cards have increased in power consumption.

There are quite a few PSU reviews by him at anandtech, and to the best of my knowledge, those test are the only (english) ones available on the web which are done by a professional using professional (= multi-buck) equipment. The latest tests are about one year old, as the guy went on to work for a big PSU manufacturer, but quite a lot of the tested models are still available today.

And here is PSU calculator that spits out figures that actually make sense, though they are still a bit on the high side. The one from newegg is not only "not completely accurate" its just plain nonsense. Either to trick you into buying a way oversized PSU, or to cover their behind from getting sued when one of those "el cheapo" PSUs blows up in your face when loaded with anything remotely close to its rated power

 

[Tarkhan]

when it comes to buying PC parts, never buy the most expensive and never buy the least expensive.

 

[Genocidicbunny]

3. Top quality brands: Stick with a top quality brand unless you're building a very low end system that will be running at stock (i.e. all low end components); then even a notorious Rosewill PSU is acceptable to keep costs down.

Never, never go with low-end PSU's. If you cant afford a better one, save up until you can. PSU is one component you should not, nay, for the sake of all your other parts, must not compromise on.

 

[GoodGame]

;9514054This article is a few years old, but still very relevant, as most components today consume rather less power. More or less only the most expensive video cards have increased in power consumption.

On this note, anyone have a link on a current brand-watch, to see which brands have improved, or tried to cash in on crap model using their name brand?

 

[Fëanor]

Antec's Earthwatts: The ones built by Seasonic were pretty decent, the ones build by Delta are not so quite. Delta is able to manufacture good PSU's but Antec is demanding lower costs which can only be achieved with inferior quality components.

 

[GoodGame]

Question about the term "Continuous Power Supply"----does that alter the normal efficiency curve for a PSU? Meaning if it's only rated at 400W is its maximum efficiency higher than just 400/2 = 200W?

An example: Antec Earth Watts green (not sure who the actual sub-contractor was though).

http://www.newegg.com/Product/Produ...-111810-Index-_-PowerSupplies-_-17371034-L02A


EDIT: Not quite sure, but I think the answer to my question is "Yes", or at least "kind of yes".
http://www.antec.com/Believe_it/Events/us/Continuous_Power/

 

[GoodGame]

Pretty useful article about the evolution of power supply unit cables: http://www.playtool.com/pages/psuconnectors/connectors.html#atxmain20

Not as useful if you're buying all modern, but useful if you still have 20+4 PSU. It corrected my mistake of using a 20->24 converter when I should have just put the 20+4 into the mobo's 24 pin header.

 

[ecuwins]

Here's a ton of PSU articles and reviews - http://www.overclock.net/power-supplies/715889-psu-articles.html