A good one can boost performance, while a crappy one will degrade performance, and eventually lead up to the failure of your computer.
(this article was originally written, by me, in vBulletin, on www.computercreators.com. If there are any dead tags that are not compatable with phpbb, please edit them or send me a PM and I'll edit them. )
How is the wattage determined? To determine that, you need to know what rails are. Rails are well regulated voltage lines, usually -12v, -5v, -3.3v, 3.3v, 5v, and 12v. You will see some crappy psu's (Demon 580w, for example) which give you what looks like HUGE amounts of power, in this case, 580w. A favorite trick of PSU manufacturers is to inflate the +3.3 and +5v rails, which gives their supply what looks like a large amount of power. Considering you don't particularly need 58a on the +3.3 rail, where you really need it is the +12.
Also important is the amount of Amps on the rails. Generally speaking, you will want at least 18-20 amps on the +12 rail. Usually, the PSU will have a +3.3v and +5v total output. You want this to be less than half of the total output.
ATX Spec: Most psu's today are ATX. That means some of the following:
-Maximum drop of 5% (that means in order to be in spec, the 5v rail must not drop any more than .25, or go above by .25)
-Hi Pot: No, it isn't a stoner's delight. It's the test that makes sure that if the psu shorts out, you will not get a shock from when you touch your case.
-Overvolt protection: Auto-shutoff if your computer is stressing the psu too much.
-24 pin connector: ATX 2.0 spec only. Required for most AMD K8 and Intel Prescott motherboards. (K8 = Athlon 64, Opteron. Prescott = Intel 5xx, 6xx, 8xx processors)
Psu calculators: Use these as a ROUGH GUIDE when calculating. Don't forget to add 20% + to the rating they give you, just to be sure you will have enough. http://www.jscustompcs.com/power_supply/
AGP Video Card 30W – 50W +3.3V
PCI Express Video 50W – 100W +12V
Average PCI Card 10W +5V
DVD/CD 20W – 40W +5V and +12V
Hard Drive 10W – 30W +5V and +12V
Case/CPU Fans 3W (ea.) +12V
Motherboard (w/o CPU or RAM) 50 – 100W +3.3V, +5V, and +12V
RAM 8W per 128MB +3.3V
Pentium III Processor 38W +5V
Pentium 4 Processor 70W – 100W +12V
AMD Athlon Processor 70W – 100W +12V
So which PSU is right for you? First: Determine how much power you really need. Don't go with a PCP&C 1KW to power a sempron. Don't look too much at the watts as much as the amps. Look past the fancy windowed mirror case, modular cables, sleeving, and UV connectors. You want a quality unit that will not blow up in your pc, killing everything.
First: the list to avoid. List shamelessly ripped off from Hardocp, but with some revisions.
Aspire I wouldn't touch this power supply with a 50 foot pole. It doesn't meat ATX spec, the rating scales are nonexistant on this supply (no temperature measures, accurate amps, wattage jump). Lots of people seem to want one cause they're bling bling. Don't. Doesn't meet basic safety spec.
Coolmax: OK power supplies, but far from the best.
Demon: Made by Powmax. Possibly one of, if not the absolute worst manufaacturer of PSU's. See below.
Deer: Makes L&C power supplies. See below.r />Devanni.
Kingwin: The ones included with cases are crap the ones that are sold seperatly are ok.
L&C: Made by Deer. Your typical craptastic generic psu that doesn't put out enough amps, and dirty power.
MGE: Same OEM as the Ultra X-connect (Taiwan Young Year). Doesn't meet required
Powmax: The absolute worst Power supply manufacturer in the world. Ever see a PowMax 450w get beaten by an Antec 250w? How about the 12v that is rated for 20a, but it blows before it even hits 17? Avoid at all costs.
Thermaltakes: Not so bad as some of the above, but still pretty damn bad. The PurePower 680w rating is mostly from the 3.3+ and 5+ rails, not the 12v, where it counts. If possible, get something else. If not, then settle for a higher end.
Ultra X-connect: Early production models (2004) made by Wintech. Starting from 2005 onwards, the OEM switched to Taiwan Young Year, and the new ones just plain SUCK. Avoid. The X-finity's are fine though.
X-superalien: Made by Powmax. See above.
DO NOT buy any of the above.
Here is a list of the good, and some descriptions.
Antec: Sometimes silent, sometimes not. Pretty reliable, but quality seems to be going downhill. Still an extremely good deal.
Akasa: Same OEM as Silverstone
Enermax: Good, silent power supplies. Quality seems to be slipping a bit, but still right up there.
Fortron (FSP): Damn good deals, and some of the best psu's I've ever seen.
OCZ: Powerstream is the second best PSU you can buy, right behind the PCP&C 510.
Sunbeam: Good, cheap, modular. SLi certified.
PCP&C: The best psu's ever. Military Spec. Silencers made by FSP.
Zippy: A bit on the expensive side, but right up there with PCP&C
Coolermaster: No Active PFC, but still a decent supply
Sparkle: OEM'd by FSP
Silverstone: The 650w Zeus is a very good supply, if not a bit loud.
Seasonic: Very, very good power supplies, and very quiet at that.
SilenX: OEM'd by FSP
Xclio: Same OEM as Antec
OK psu's, better than some, not as good as others. If possible, get something else. Still a good reliable unit. Orion series isn't great.
If you plan on running SLI, consider one of the following
These are the Sli certified supplies. Official list from nVidia. I have crossed out several supplies which I do not feel should be part of the list, for reasons ranging from reliability, compatability, and just lack of power.
Akasa PowerPlus 650W PSU
Akasa PowerPlus 550W PSU
Antec NeoHE 500W
Antec NeoHE 550 Uncompatable with Asus A8N-sli, and dies if you think too hard.
Antec TrueControl II 550
Real Power 550W SLI
CW-650T 650W Extreme Power Reletivly unreliable, and overpriced.
Enermax EG565P-VE FMA 535W
Enermax EG651AX-VH EPS12V 550W
Enermax EG851AX-VH EPS12V 660W
Enermax EG701AX Noisetaker 600W
EPSILON FX600-GLN 600W
EPSILON FX700-GLN 700W
Type-R series 580W HPU-4[B,K,R,S]580
PC Power & Cooling Turbo-Cool 1KW
PC Power & Cooling Turbo-Cool® 510 SLI (510ATX-PFC)
PC Power & Cooling Turbo-Cool® 850 SLI (850ETX-PFC)
Seasonic S12-500 Watt
Seasonic S12-600 Watt
Silverstone ST65ZF 650W
Silverstone ST60F 600W
Sparkle Power FSP550PLG-SLI 550W
Sunbeamtech NUUO Series 550W SLI (SUNNU550-US)
Ultra Products X-Finity 500 Watt PSU
Ultra Products X-Finity 600 Watt PSU
Zippy Gaming GSM-6600P(G1) 600W
And a psu Not on the list, but VERY highly recommended for SLI:
OCZ Powerstream 520
OCZ Powerstream 600
These aren't on the list because, even though they are easily capable of exceeding the spec, OCZ does not want to pay the royalties.
So, consider the following psu's, listed in order from good to best.
$40: Fortron 400W
$52: XClio 450BL 450W
$79: Enermax 535W SLI-Ready
$125: OCZ PowerStream 520W
$239: PC P&C 510 ASL
Seasonic S12 430/500/600w is made for you, if you insist on quiet pc's.
Best bang for buck:
$39.99FSP Group (Fortron Source) AX400-PN ATX12V 400W
[email protected] ([email protected] total max)
$52.50 XCLIO XClio 450BL ATX 450W
$66.99 Antec SmartPower 2.0 SP-500 500W
$72 Fortron 500W Blue Storm AX500-A ATX12V:
$79 Antec TRUEPOWERII TPII-480 BLUE ATX12V 480W:
$83 Enermax 535W Whisper II EG565P-VE FMA V2.01 - SLI Certified
+12V: 34A (total)
$87.00 Antec TRUEPOWERII TPII-550 550W
Those are the best psu's in their class. If you want an SLI Power supply, and don't want to buy a PCP&C 1KW, and prefer to spend a bit less, these are what you want.
If you want a bit more power, and willing to spend a bit more, keep reading.
All PC Power And Cooling Power supplies. Just be aware: The Silencers are made by Fortron (FSP)
$79.00 Sunbeam NUUO SUNNU550-US-BK ATX12V/ EPS12V 550W
$86.99 OCZ PowerStream 420W Power Supply Model "OCZ420ADJ"
Model# OCZ420ADJ Item # N82E16817104150
$119 Thermaltake W0057 PurePower 500W Power Supply - Retail
$105 OCZ PowerStream 520W Power Supply Model "OCZ520ADJ"
[email protected]>[email protected]
$183 OCZ PowerStream 600W (700W Peak)
[email protected], [email protected], [email protected], [email protected]
$89 for ModStream 520W
$74 for ModStream 450W
SeaSonic S12-430 ATX12V 430W
MTBF >100,000 Hours
$124.95 SeaSonic S12-500 ATX12V 500W
$130 SeaSonic S12-600 ATX12V 600W
$83 Antec NeoPower 480W Modular 120mm fan ATX 12V v2.0 power supply (VERY VERY good psu)
$129.99 Hiper Modular Type-R 580W Power Supply (630W Peak)
ENERMAX Noisetaker 600W Power Supply, ATX 12V V2.0 compatible
$85.49 shipping Sparkle Power 550W Power Supply, MODEL "FSP550-60PLG" -OEM
Model# FSP550-60PLG Item # N82E16817103478
$98 & shipping Antec 550W Power Supply, 24-Pin, Model "TRUE550 EPS12V" - Retail
MTBF: 80,000 hrs. @ 25ºC
$469 PC Power and Cooling Turbo-Cool 850 ETX (SSI) - 850 Watts of Power at Load!
850W continuous and 950W peak power
+3.3 Volt @ 30 Amps
+5.0 Volt @ 30 Amps
+12V1 Volt @ 17 Amps
+12V2 Volt @ 17 Amps
+12V3 Volt @ 17 Amps
+12V4 Volt @ 17 Amps
-12 Volt @ 0.8 Amps
+5 VSB @ 2.0 Amps
That PCP&C 850 is easily the second best PSU you can buy, right behind the 1KW. 4 17a 12v rails.
What if you want silence? Try the following...
Antec Phantom 350w
Antec Phantom 500w
SeaSonic S12 380/430/500/600w
(shamelessly stolen from www.jonnyguru.com)
First; do you have a Socket A CPU? If so, does it have a 2x2 12V connector? If not, you can stop reading after a few as the bulk of this text simply does not pertain to you. Your CPU’s core voltage is regulated off of the power supply's 5V rail and you’re putting as much as a 15A load on the 5V rail just for your CPU. This means you should rule out a few things when looking for a power supply:
Socket A board without a 2x2 12V connector:
Do not use a dual 12V rail power supply. One of the two rails on a dual 12V rail power supply is for the 2x2 connector, so your power supply will have a rail you're not even capable of using!
Do not get a power supply with a higher amperage on the 12V rail than on the 5V rail. I know future-proofing is a usually a good thing to do, but typically when a power supply with a high 12V capability is hit with a heavy 5V load, even when it's within spec, there's a thing called "crossloading" that happens. Essentially, your 5V dips below tolerance and your 12V shoots above. Side effects include lock up or even system shut downs due to over or under volt protection!
Now for the rest of you... You have a 2x2 12V connector on your motherboard, which means your CPU regulates it's core voltage from your power supply's 12V rail.
This is where I prove to you why you shouldn't go by the wattage of a power supply...
Let's start with a base system of an Athlon XP 3200+ and a high end AGP video card without an auxillary power connector (like an nVidia 6600.) Even if all you have is a single hard drive and a single optical drive.
You're going to need a power supply with at least 17A on the 12V rail.
This number is pretty low because AGP cards get a lot of it's juice from the 3.3V rail via the AGP slot. But the AGP slot is only capable of supplying so much voltage. So what if you want a more powerful video card?
Let's say you have an AGP video card with an auxillary power connector (like a 6800.) The power connector supplies up to an additional 6.25A of 12V to the video card. So now we should look for a power supply that has more juice on the 12V than our initial build.
You're going to need a power supply with at least 24A on the 12V rail.
Adds up quick, doesn't it?
Now let's say you have a Pentium 4 and an AGP card instead of an Athlon XP. Or that you have more drives, PCI cards and some fans other than the CPU fan.
Add 2.8A to the 12V rail for Pentium 4 processors. Add 3.4A to the 12V rail if the Pentium 4 is a Prescott.
Add 1.5A to the 12V rail for each additional hard drive.
Add 1.5A to the 12V rail for each additional optical drive.
Add .5A for each fan in your system.
Add .5A for each PCI card in your system.
Now let's do some builds with PCI express video cards.
Since Socket A chipsets don't support PCI express video cards, we're going to switch the CPU in our base build to an Athlon64. That has a 7.4A requirement on the 12V rail instead of the 6.4A of the Socket A CPU. The PCI express slot can handle more juice and the PCI express card gets most of it's juice from the 12V rail. So our numbers change a little bit.
18A is enough juice on the 12V rail if you have a single PCI express video card without an additional power connector.
24A is enough juice on the 12V rail if you have a single PCI express video card with a connector for additional power.
Add 1.75A if your Athlon64 CPU is an X2 model
Add 1.8A to the 12V rail for Pentium 4 processors. Add 2.4A to the 12V rail if the Pentium 4 is a Prescott.
Add 3.4A if your Intel CPU is a dual core Pentium D
Add 1.5A to the 12V rail for each additional hard drive.
Add 1.5A to the 12V rail for each additional optical drive.
Add .5A for each fan (other than the CPU fan) in your system.
Add .5A for each PCI card in your system.
Now we get into dual PCI express video cards. Let's say you're using SLI or ATI's Crossfire. One would think that two video card means twice the power requirement, but that's actually not true for the same reason as your performance not doubling when you have two video cards. The additional power requirement for the second video card is still fairly significant, though.
Add 4A if you have a pair of video cards and neither of them have their own power connector.
Add 6A if you have a pair of video cards with a power connector for each.
Dual rails: Explaination
Why do some power supplies have dual 12V rails?
Now that I've convinced you to quit looking at the total wattage of a power supply and to start looking at individual amperage ratings per rail; I need to explain the power supplies with dual 12V rails.....
With the demand on +12V becoming greater and greater, Intel decided it would be "safer" to split the duty of supplying +12V across two rails. It's "safer" because inexpensive transistors capable of supplying more amperage (say more than 34A) at any kind of decent efficiency (70% or better) are subject to blowing up. :-) That's not very safe. ;-)
To split the duty up between two (or more) +12V rails, one can use cooler running, cheaper transistors to supply the power. Furthermore, this isolates devices on one rail from another, so EMI introduced by lighting inverters and drive motors can be isolated from sensitive components like the CPU and video card.
(14 * 12) + (16 * 12) = 336? What is this? NEW math?
You'll often find that the capabilities of the +12V rails combined almost never equal what is listed for each rail individually added together. This is because, although the two +12V rails are on separate transistors, they're still being fed by the same, single transformer and rectifier. So one rail might be able to pull off 168W if loaded up by itself, and the other might be able to pull off 192W if loaded up by itself, but the amount of juice that can even get to those transistors (safely) isn't more than 336W, so you simply CAN NOT fully load both rails to their maximum capabilities. And when I say "can not" load them, I mean load them without overloading them and staying within the tolerance of the rated rail. I mean, I put 16A loads on 14A rails all day long... that doesn't mean it's recommended.
Again, that part is pulled directly from jonnyGURU.
Now a bit more:
Rankings from absolute WORST to absolute BEST. I've seperated them into groups.
Dynapower (they even have bogus UL numbers on them!)
Raidmax (the ones that come bundled with a Raidmax case. Not necessarily one you'd buy separately.)
Turbo Links that are made by "Real Power" (like the ones that are included inside Aspire cases.)
Rosewill (various manufacturers, but usually fair quality.)
Coolmax and some other ATNG manufacturered units.
Low end Wintech's (like Ultra V-Series and some Turbo Links)
FSP Saga series (AX part number)
Youngyear (includes some older Ultra X-Connects, MGE's and Aspires.)
Enlight (used to be Enhance, but now seem to all be ATNG's)
FSP/SPI (those with FSP part numbers.)
Topower P5 based units (like OCZ Modstream, Tagan, most ePowers.)
Most Wintech (most Ultra models, Sintek, Future Power, some MGE's)
Topower P6 based units (like the OCZ Powerstream.)
AcBel Polycom (Coolermaster, for example.)
Sunbeam NUUO series
PC Power and Cooling Silencer series
Enhance (includes some Silverstone units)
PC Power and Cooling Turbo-Cool series
Etasis (includes some Silverstone units)
Only good psu's listed for obvious reasons
True series (TruePower, TrueControl, etc etc): 21.3 DB
NeoHE: 18 DB
Phantom: Nearly Noiseless (no fan on the 380, fan on the 500 only spins on high loads, but the actual electronics buzz)
Smartpower series: 20db average.
Neopower 480: 35 db
Paxpower: 18 db
650w (dunno the name) 21.3 db (Doubtful, its the same innards as the silverstone zeus and that is loud)
Noisetaker: varies between 21 and 44 db depending on load
Green: under 30db
zen (300w only): 0 db (fanless)
Blue Storm: under 30db
Powerstream: <22db (I have one, and it is truely quiet and stable. Highly recommended)
Modstream: couldn't find it, but I'm sure it's quieter than 22db because of the single 120mm vs 2 80's
510, 850, 1kw: Louder than ****. They have Delta's in them.
Silencer series: 24 db
No info found.
zm series: 20db
Most about 25 db (no info found)
Realpower: 23 db
stealth: 47.5 db-53.7 db (Loud. Don't be fooled by the name)
Zeus: see Akasa
nightjar: 0 db
Same innards as FSP, but only with super silent fans. Approx. 18 db
See Antec. Same OEM (channelwell technology)
So, who makes whose power supplies? Remember, most brand names do not make their own supplies. They slap a label onto a supply (basicly), and sometimes a few modifications to it.
some Scythe models
silverstone Zeus ST56ZF, upcoming ST75ZF, and the fanless unit
Chieftec (the 420w unit, at least)
Ultra (except x-connect v. 1)
Raidmax (the ones included with cases)
Kingwin Absolute Power
Viper (the ones at bestbuy)
some Wintech branded units