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Offline Ramman  
#1 Posted : Monday, June 21, 2004 1:13:16 PM(UTC)
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EDIT 1/31/05:

Our little baby has grown up over the past few months. So it's time to change it from a basic knowledge thread to a full blown guide.



There have been a multitude of PSU related questions lately. I'll put this up as a stickey. If anyone has anything to add, feel free to do so.

The PSU (Power Supply Unit) is one of the most misunderstood and overlooked pieces of hardware. It seems that most everybody looks for the latest and greatest in motherboards, CPUs, video cards, etc. When it comes time for the PSU, hey any ol' thing will work. Not so, the PSU is very important. Read on.

When the PSU is working properly, we tend to forget about it. Hit the power button and off we go. What happens when you hit the button and are greeted with silence? The first thing most of us blame is the motherboard. When the first thing we should look at is the PSU.

A bad PSU can cause random shut downs, premature failure of other hardware, or complete meltdown of your system. Poor voltage regulators will cause spikes or fluctuations that will lead to hardware failure or spotty performance. Lack of overlaod protection can cause your system to be a miniature Chernoble.

The modern PSU has three main voltage legs or rails, 3.3V, 5V, and 12V. There are also negative voltage rails. These are used mainly as reference voltages for various cards. The main concern is with the positive rails.

Well then what do we look for in a PSU? Don't be confused with a PSU rating of total wattage. Look instead at the amperages for the 3.3, 5, and 12V rails. For todays systems a minimum requirement should be as follows:

3.3V - 25AMPS
5V - 25AMPS
12V - 20AMPS

Again, these are MINIMUM. You can't over-power your computer, only under-power. Keep in mind what video card you are going to use. nVidia's FX series and above, and ATi's 9700 and above are power hungry. Most require a separate power source other than what is supplied from the AGP slot. This means a lead from the PSU must be hooked to it.

Shop by the Pound. Sounds strange doesn't it. But it's more or less true. This goes back to the cheaper PSU's using smaller heat sinks. An aluminum heatsink will weigh much less than a copper one. Just an examle; the A-Power 450watt PSU weighs in at just under 2.5 pounds. The Antec 480 weighs in at just about 5 pounds. They both have 2 fans, case size is the same, and the 30watt difference wouldn't require a 2.5 pound heavier heatsink. The simple truth is the A-Power uses much smaller and lighter heatsinks.

Do not buy generic PSU's no matter what the rated wattages are! These types of PSU's over-rate their supplied wattages among other things. So a PSU that states "400 watts" may only put out 350 or less. They also use cheap heatsinks which will lead to a meltdown. Voltage regulation is poor to say the least. So who is cheap? The following are supplies you should avoid:

Mustang, Powmax, MGE and A-Power are in the sub $30 range and will fail. I've seen these fail within days of being installed. Another one to add is Q-tec, as it seems this is another one people have had problems with. Tagan has been added to this list for various reasons.

So who do we trust? The following list are manufactures of quality PSU's. These are not cheap, money wise. I will list a couple of "economy" supplies that I know to work rather well. These are still much more than those listed above.

Enermax, Antec, Thermaltake, Zalman, PC Power & Cooling, Superflower, Nexus, Fortron Source, Seasonic, OCZ. (Note: Tagan has been removed from the approved list due to poor performance and customer service suffered by several members. I hope these issues are cleared up by Tagan soon.)

Economy:

APEX (used to be Allied), Sparkle, AHANIX, Rosewill (Newegg house brand)

This was just a basic overview of PSU's. But, should give you enough information to be able to choose a suitable one for your system.

EDIT (1/3/05)

PCI-E Cards

Now that PCI-E, and the resulting vid cards are here, we need to look at how to power them. The low-end cards do not require a separate power source. They are quite happy with the power supplied by the the PCI-E bus. However, don't let this fool you. I've seen some sites say that 300 watts is plenty to power these cards. Well, they might be right if you have a very generic system. But just add another HDD, a couple of optical drives, more RAM, a fan, case lights...you get the picture. A 300watt PSU will lay down and die with that load. Just be careful what you read and take it with a grain of salt. Look at what you want to power up now, and what you might want to add later.

The high-end PCI-E cards still require a separate power source. So our recommendations remain the same as high end AGP cards. However, PCI-E cards use a different power connector. You will need an adaptor if your PSU doesn't have the new style.

OK, let's look at SLI. Now you have 2 vid cards to power, along with everything else. So your 450watt PSU that looked good six months ago, is now looking a bit weak. If you are looking at high-end cards you will need separate power sources. If you don't have the new connectors, you will need four molexes to power the cards.

So now not only do you need to look for a quality PSU to handle the load, but one that has adequate molex connectors as well. Just to put your mind at ease, most quality PSU's have more than enough connectors to fit your needs. Just check to see if PCI-E connectors are included. This is one area where our recommended economy PSU's will lack. Of course, if you're going to the expense of running a SLI setup, I hope you planned not to use an economy PSU!

---------------
EDIT: *addition by Ray * btw, excellent post great one!

*A good way to monitor your PSU is using a program called speedfan, there are many others but I like using this one the best.

*When a PSU goes bad, it can take other hardware peices with it. I've had it take out 2 of my WD 80gig SE hard drives out at once. Never settle with a cheap PSU!!!!

*Many were probably waiting for this... TTGI (super flower) is my brand of choice when it comes to inexpensive PSU's... PC Power and Cooling is the best but expensive

Thats all
------------------
Offline Jordan  
#2 Posted : Monday, June 21, 2004 2:14:51 PM(UTC)
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Power Consumption
This article is a guide on how much power a top end system will require and why it is important to consider power consumption when deciding on what PSU to purchase. Power Factor Corrections, general buying advice and the top quiet PSUs are also covered.

Key:
Power (P) is measured in Watts (W) and is the overall maximum output across the 12V rail and the 3.3/5V Rails.
Current (I), measured in Amps (A), is what rating individual rails are given to show their capacity.




High end systems
This section specifies how much a top end system will use. If your system isn't going to be top end remeber that you won't need as much power but always think about upgrades. With manufacturers now focusing on reducing temperatues (since air cooling has pretty much maxed out) with 90nm chip technology etc I don't see power requirements moving up much in the future. Manufactueres are becoming more sensible now the limits of air cooling have been reached.


This article from The Tech Report shows the power consumption of high end systems with a high spec graphic card (6800GT):

The Tech Report article

Test system specs:

OCZ PowerStream 470W PSU
P4 3.4GHz
6800GT
1GB of Corsair XMS 3200XL
Maxtor MaxLine III 250GB SATA HD
Asus DVD-ROM

Idle: 151W
Load (Xmpeg): 236W

The above tests are with strain on the CPU only so don't show the strain on a PSU under intense gaming loads like Doom 3.


The following report from X-bit labs shows the power consumption of the latest graphics cards under stress:

X-bit labs article

The difference between the 6800GT idle and the highest single power draw from all the cards tested under load works out to be around 50W. These tests show the power consuption of a 6800 Ultra under load to be less than 80W. In fact, they show it to be less than that of the 5950 Ultra. So to those of you worrying about getting a 480W+ unit to accomdate a 6800 Ultra, as long as you get a GOOD BRAND (see recommended brands above) 400W or over you are fine for any upgrade.


Top end system:
80W max - 6800 Ultra under load
110W max - The lastest P4E under load - Less for P4Cs and A64s
20W max - per HD (even the Raptors use under 15W, the only ones I know that use 15W+ are Seagates)
~60W - RAM, any PCI cards, Motherboard, optical drives, fans, and any host powered devices (estimate)



Rails (additional)
Although tthe above is all true for power consumption, on a simple level there is also a need to pay attention to individual rails (as Ramman states above). Before the latest CPUs and graphics cards things were much more simple but now depending on your graphics card and CPU, your system could really need a lot of current (Amps) on a particular rail(s). Here's a little you might want to know before you go for a PSU that suits your power requiremennts:

The latest CPUs (AMD and Intel) draw a lot from the 12V rail, this is why the aditional 12V 4-pin plug was introduced.

The latest high power graphics card require a molex plug(s) to give them extra juice as they simply can't draw enough from the AGP/PCI-E slot alone (which takes it's power from the 5/3.3V rail). As a result these cards also draw quite heavily on the 12V rail which is already supplying the CPU and some drives' power.

If you are buying a system with a high powered graphics card and CPU then pay particular attention to the 12V rail.

If you are buying a system with the intent of SLI also then make sure you have plenty of current (Amps) on the 5V rail and you should really be looking at a PSU with dual-12V rails.



Conclusion:
Total power consumtion for a TOP end system = ~300W for a high spec PC like the one above with a couple of HDs (350W PSU absolute min RECOMMENDED for this set-up)

Overclocking - add another 100W max for good measure if you plan on pushing to the extremes on air = ~400W (400W min recommended for the above set-up and OCing). The only reason you might need more is if you are using water/TEC cooling and pushing OCing even further.

If you have a high power CPU make sure to get a strong 12V rail. With a high power graphics card on top of that make sure you have a strong 5V rail too. For SLI I strongly recommend a PSU with dual-12V rails. The Enermax Noisetaker and Seasonic S12 share my PSU of choice award across their power ranges'. These PSUs have dual 12V rails, (excellent for high speed CPUs and SLI as above), are very quiet and also include a 20-24pin ATX convertor for 24-pin ATX type Motherboards (see below). Complete range up to 600W! (NO NEED for 600W, 430-485W is plently for realisticly ANY set-up)

Remeber the key is QUALITY!



How to save money
The main reason people avoid quality PSUs and opt for the cheaper non-branded option is obvious - price. However skimping on the PSU is, along with the Motherboard, the worst area you can possibly compramise in since a bad PSU can take out other components when it blows.

A good way around this is if you are buying a new case and PSU is to opt for a case/PSU combo from the likes of Antec, Aopen and Thermaltake. All three make excellent cases and PSUs and buying both together saves a lot of money.

Here was my reply when someone asked about buying a cheap case:

"Well cases are pretty much similar. A more expensive one will be solid and heavy and have a general quality about it. It will also usually look better and it'll be nice and easy to work with and will have rounded edges so you don't cut yourself. A cheap case will be light and suffer from resonanace (vibrations, amplifying noise from HDs, optical drives, fans etc) and there's good chance you'll cut/hurt yourself on the sharp edges while you're working on it.

But ultimately a cheap case will still "work" the same as any other case, it's just not as fun to work with. What you need to make sure is, with a cheap case, that the air intakes and exhausts are open, and not obstructed, so air can flow easily. You also have to make sure you have spaces to mount fans and also that fans come included (or you'll have to order some adding to the cost).

Just never get a cheap case that includes a PSU is the absolute rule. Unless you REALLY like the case and plan on dumping the PSU."

Just want a PSU? If you are from the US and shop at Newegg - As a low power replacement (300-350W) I recommend Fortron (FSP) or if you are looking for something with a little more power then Thermalakes PurePower range. If you are from the UK Thermaltakes seem to be more expensive than other brands over here but Fortron are still the budget choice. Also look out for Enermax Noisetakers at a good price for a real quality bargain.



Active/Passive Power Factor Correction
Someone recently asked about PFC (Power Factor Correction) so here's the lowdown.

Active PFC means the PSU has a circuit to correct the power factor. What this does is improve the efficiency of the PSU. The benifits of which are saving you a little on your electricity bill and it should mean the PSU runs cooler as there is less waste heat generated. It is more expensive to build an Active PFC PSU so these units tend to be more expensive. Remeber though that just as not all PSUs are created equally, not all APFC PSUs are either

Passive PFC means the PSU uses a capacitive filter at the AC input to correct the power factor. Again this imporves efficiency over non-PFC but isn't quite as effective as Active PFC. It also, to a slightly lesser extent, has the same benifits.

Non-PFC - Well all PSUs should have either APFC or PPFC these days, in fact PFC (active or passive) is a REQUIREMENT under European legislation. But you Westerners are happy to use resources willy nilly so it's not a requirement there yet...



Quiet PSUs
This section will apply to anyone that is bothered by the noise their system makes (like me) or is interested in making a Media/PVR/HTPC machine:

Just because a manufacturer has the word quiet in the usual marketing lingo don't belive it! Also don't pay much attention to manufacturers dBA ratings (especially not when cross comparing different manufacturers as there are not set standards for measuring), even if it is a top brand.


The best PSUs for a quiet system are ranked below in order from best (left) to next best alternative (right).

up to 350W - Seasonic S12> Enermax Noisetaker> Nexus NX3500
up to 400W - Seasonic S12> Antec Neo HE> Enermax Noisetaker> Nexus NX4090
Above 400W - Seasonic S12> Antec Neo HE> Enermax Noisetaker - these PSUs all feature dual 12V rails, excellent for high speed CPUs and SLI (as above), and include a 20-24pin ATX convertor discussed below.

*NO NEED for 600W PSU, 485W is realisticly enough for almost ANY set-up. The higher powered units are usually louder, as they tend to ramp fan speeds up quicker as temps rise, and they also run with less eficciency at lower power loads.

Fanless - ONLY Antec Phantom 350W & 500W (hybrid) get my recommendation, every other fanless PSU I've read about has suffered from random restarting and boot up problems due to heat. *With fanless PSUs good case airflow is essential which I feel defeats the purpose and hence, I don't recommend fanless PSUs at all*



The Future?
This is really just down to my own views but I don't see opting for a 480W+ PSU "planning for the future/future upgrades". The reason I disagree with this is that the trend of chip manufacturers now is trying to reduce power loads since air cooling has pretty much reached it's limits. With 90nm CPUs and Intel taking focus off higher clock speeds and more efficient chips I don't see power load increasing much in the near future.



Additional

Proprietary PSUs - Dell, Compaq, Emachines, HP, Gateway and others use proprietary fittings on their PSUs and Motherboard. Although soetimes the power connection for an aftermarket PSU may fit the Motherboard it may be wired differently and may even damage other components if it is powered up. If you wish to upgrade your propritary Motherboard then I'm affraid to say it likely means you'll have to upgrade the PSU (for both fitting, and likely, power reasons). If however you are looking to replace a PSU the information in the following thread may be helpful: proprietary solutions

24-pin ATX - New Motherboards inc nForce 4 SLI and new Socket 775 boards require the new 24-pin type ATX connector based on the BTX spec as opposed to the previously more common 20-pin ATX type. If you are in the market for one of these boards then try and get a PSU that includes the 24-pin header or at least comes with a 24-pin convertor. If the PSU you have your sights on doesn't, or if you already have an existing PSU you are planning on keeping, then I advise you invest in a 20-pin to 24-pin ATX adaptor. It is possible to plug a 20-pin ATX cable straight into a 24-pin socket but if you are unsure of this use an adaptor. Alternatively there are 24-pin to 20-pin ATX adaptors available for those of you with new 24-pin PSUs and older boards.
Offline Ramman  
#3 Posted : Monday, June 21, 2004 4:15:23 PM(UTC)
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I've heard some stories about Q-Tec as well. Some are good some are real bad. I've not used them before, but I trust you. If you say these are bad, that's good enough for me.

PC Power and Cooling, yep forgot about them
Offline thedazman67  
#4 Posted : Monday, June 21, 2004 5:33:11 PM(UTC)
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During the early stages of when i built computer system i used Q-tec power supplies in out of the 5 systems i installed them in 3 of them failed within 3 months.

thedazman
Offline S2  
#5 Posted : Wednesday, June 30, 2004 10:29:20 PM(UTC)
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You guys forgot Fortron and OCZ!!! Add em up there.
Offline Ultragamer  
#6 Posted : Thursday, July 1, 2004 12:36:50 PM(UTC)
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Hmmm..... I bought a powmax case, and it came with a 400W power supply... so you think I should chunk it and get a different one???
Offline Jordan  
#7 Posted : Thursday, July 1, 2004 12:48:08 PM(UTC)
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I'm not to sure about Powermax. Do they make their own PSUs or just bundle generic ones with their cases? Check the PSU for a brand name on the sticker.

What kind of set-up do you run? A high performance rig will need better than a 400W generic for sure.
Offline mentaldisorder  
#8 Posted : Thursday, July 1, 2004 7:48:44 PM(UTC)
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Powmax makes their psus
Offline Jordan  
#9 Posted : Thursday, July 1, 2004 7:51:23 PM(UTC)
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Thought that was the case so I never wrote it off as unbranded. Do you know if they are any good?
Offline mentaldisorder  
#10 Posted : Thursday, July 1, 2004 8:15:03 PM(UTC)
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i believe it was ramman that stated that they were a piece of crap...hang on ill find the thread i made on em

[edit] here it is...http://www.pchardwareforum.com/...ad.php?s=&threadid=20152
Offline Jordan  
#11 Posted : Thursday, July 1, 2004 8:47:16 PM(UTC)
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Oh yeah Powmaz are already in the avoid list anyway
Offline Ultragamer  
#12 Posted : Thursday, July 1, 2004 8:57:02 PM(UTC)
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so that means it is not that great of a power supply huh? How big of a PSU do I need if I get another one, another 400W, or maybe a lil bigger?
Offline Jordan  
#13 Posted : Thursday, July 1, 2004 9:02:44 PM(UTC)
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Sorry what are your specs again? You should have a sig Or even an Avatar that I could accossiate you/your specs with.

EDIT: Ah you have a image sig (it doesn't show up for meunless I click the ink). 2.8GHz and 9800 Pro should be OK on 400W but you might want to go higher for any future additions/upgrades. Try Thermaltake, cheap and don't really do under 400W
Offline Ultragamer  
#14 Posted : Thursday, July 1, 2004 9:24:26 PM(UTC)
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Oh, yeah sorry about that, i forgot to tell you my spec's. I didn't know I had that link of there, i guess you learn something new everyday. Hmmm.... alright, i am glad you think it would be okay, because i don't really have the extra money to spend on a extra psu, I need to get a few more important things like cpu, and video card. I found a "Thermaltake Silent PurePower, 420W ATX power supply.UL, CSA, TUV, CE Approved. Intel Pentium 4 Compliant for $38, and a Thermaltake W0014 Silent Purepower 480W with Black housing - Xaser Edition ATX 2-Fan Power Supply for $55, just in case.
Offline Jordan  
#15 Posted : Thursday, July 1, 2004 9:26:59 PM(UTC)
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Wow $38, now that's what I'm talkin' about

If you want to spend the extra $17 for future upgradeability go for it, if not the 420W will be plenty for your current set-up.
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