PSU MYTHS EVERY ONE SHOULDKNOW

[dmelsie]

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Power Supply Myths Exposed!
1. DOES A POWER SUPPLY UPGRADE MEAN A HIGHER ELECTRIC BILL?
This is the biggest myth of all. First, it's important to understand that a power supply only delivers the power that's needed by the system, nothing more. If your PC currently has a 400W supply and the system needs 350W, it will still need and use only 350W - if the only change is upgrading to a 500W power supply (the upgrade makes sense since there are many advantages to running a power supply at a lower percentage of its rated capacity). Whether the electric bill goes up or down is solely determined by the efficiency of the new power supply. Greater efficiency means a lower electric bill because more of the AC power is converted into DC for the computer, rather than wasted as heat. The savings can really add up over time. For example, when the money saved in electricity over the course of its 3-year warranty is taken into account, the purchase price of the efficient Silencer 750 is less than $0.00. Here's the math:

Model Efficiency @ 550W Input Power @ 550W
Silencer 750 83% 662W
Antec True Power 550 73.8% 745W
For the same output power, the Silencer 750 uses 83W less input power.

3-year savings = .083KW x $0.10/KWH x 24 x 365 x 3 = $218.12

2. DON'T BE MISLED BY EXAGGERATED WATTAGE CLAIMS
To properly compare power supplies, wattage claims must state the maximum ambient temperature for continuous, full-load operation. Unfortunately for the consumer, this information is usually withheld, opening the door for manufacturers to exaggerate their wattage claims. They do so by assuming an unrealistic ambient temp of only 25°C (77°F), even though the actual internal power supply temp is at least 40°C (104°F). Since the proper full-load rating is 15°C higher for home use and 25°C higher for industrial use, these power supplies produce 33%-50% less power than their advertised ratings. See the derating chart on the right.

5. AN SLI CERTIFIED POWER SUPPLY WILL ALWAYS POWER HIGH-END GRAPHICS CARDS?
We went through three power supplies before we found one that consistently worked with these high-end graphics cards and an FX-60. We initially started with a Silverstone 600W SLI certified power supply, but running some games resulted in the system powering down under full load. We next moved onto a higher rated Thermaltake PurePower SLI certified 680W unit. But while most games ran most of the time, the system would still occasionally shut down. Finally, we ended up using PC Power and Cooling's massive TurboCool 850 SSI. This just goes to show that if you really want to build something that pushes the bleeding edge, make sure you have the right power supply.
ExtremeTech Review Feb 12, 2006

6. SHOULD AN ATX POWER SUPPLY BE COOLED WITH A 120MM FAN?
Most low-noise ATX power supplies today utilize a top-mounted 120mm fan rather than a rear-mounted 80mm fan. The 120’s favorable reputation is based on the fact that under low to medium load conditions, the 120mm fan provides sufficient cooling at low RPM and low RPM fans are generally very quiet.

However, problems occur with this design when the load exceeds 50%-60%. Because the 120mm fan consumes about 1.5� of vertical space inside the PSU, heat sinks, capacitors, and other components are about 30% smaller in height compared to a PSU with a rear-mounted fan. The smaller parts can handle less current, so the maximum power available with the 120mm design is limited. And, because the heat sinks have less surface area, more air flow is needed with this design to keep the thermal situation under control. With 80%-100% load, the 120’s fan speed can double and the noise level can jump by up to 20dB.

In conclusion, for systems that require more than 50% of the power supply’s capacity, a well-engineered PSU with a rear-mounted 80mm fan will provide superior performance and reliability (due to larger components) at a noise level comparable to a PSU equipped with a 120mm fan.

7. ARE TWO POWER SUPPLY FANS BETTER THAN ONE?
No. A power supply with two fans doesn’t exhaust any more air from the case than a power supply with one. That's because due to space limitations, only one fan can be used for exhaust, while the other is limited to spot cooling. Possible explanations for a 2-fan PSU include: thermal engineering problems; an attempt to exaggerate the wattage rating by spot cooling the transformer; or an attempt by the marketing department to create a new gimmick.

8. ARE MULTIPLE 12-VOLT RAILS BETTER THAN A SINGLE 12-VOLT RAIL?
With all the hype about multiple 12-volt rails (ads claim that two rails is better than one, five is better than four, etc.), you’d think it was a better design. Unfortunately, it’s not!

Here are the facts: A large, single 12-volt rail (without a 240VA limit) can transfer 100% of the 12-volt output from the PSU to the computer, while a multi-rail 12-volt design has distribution losses of up to 30% of the power supply’s rating. Those losses occur because power literally gets “trapped� on under-utilized rails. For example, if the 12-volt rail that powers the CPU is rated for 17 amps and the CPU only uses 7A, the remaining 10A is unusable, since it is isolated from the rest of the system.

Since the maximum current from any one 12-volt rail of a multiple-rail PSU is limited to 20 amps (240VA / 12 volts = 20 amps), PCs with high-performance components that draw over 20 amps from the same rail are subject to over-current shutdowns. With power requirements for multiple processors and graphics cards continuing to grow, the multiple-rail design, with its 240VA limit per rail, is basically obsolete.

PC Power and Cooling is once again leading the industry. All of our power supplies now feature a large, single 12-volt rail. The design is favored by major processor and graphics companies, complies with EPS12V specs (the 240VA limit is not a requirement) and is approved by all major safety agencies such as UL and TUV.

[brown_dog]

Yeah, tell us something we already know...

[StyM]

nice info bro...

[Hot Ice]

Yah, this is a great read..

up tani para sa uban wala pa kita..

[goryo13]

nice one bro!

was looking for something like this... very enlightening. keep 'em coming :mrgreen:

[v2s13]

Nice one bro, nindot jd ni in ani na learnings sa PC

[dmelsie]

nakuha ko yan sa idol kong psu

[emoners]

Nice bro! :mrgreen: Add lang ko extra info:

POWER SUPPLY FAQ
source: http://www.jonnyguru.com/forums/showthread.php?t=1036

The power supply is the single most overlooked component in a computer system.

CPU's, RAM, video cards, hard drives... at a performance level, any of these components can easily cost hundreds of dollars each. Yet the one component that powers everything in your machine, and could potentially screw up everything in your machine, is still the one component most people hesitate to spend at least $100 on (there are VERY FEW acceptable exception.)

A PC power supply is one of the most important components in a computer, yet it is often the least appreciated due to its "low-tech nature". When a power supply is dead, your entire system is dead. A bad computer power supply could also cause other parts of your system to fail. As personal computers become ever more powerful, the importance of a reliable power supply is more than ever before.

A power supply that has fluctuating rails can cause lock ups, crashes, etc. The ATX standard has quite a bit of tolerance; 5%. Regulators on the motherboard and other components have even more tolerance. But when a power supply has weak rails, voltages can easily drop below these tolerances. Sometimes a multimeter can't even pick up these sags in voltage because they happen so fast. But all it takes is a sudden dip to lock up your system.

MOST power supplies have protection that prevents overvoltages, undervoltages, short circuits and high temperatures from killing other components. But just like any other component in your PC, failures are unpredictable and these protection circuits can fail. When this happens, damage can occur to components.

Picking the right power supply

Quality

Common sense is going to tell you that the best way to determine the quality of a power supply is to stick with a brand that’s known for quality products. Also, COMPETENT reviews help as well.

One indicator I’ve used is the UL number of a power supply. UL actually certifies that a product is "safe" to use within a determined operating range and environment. Although I don't believe they actually load test every power supply, cross referencing a UL number can be handy for many reasons.

You can use a UL number to find out who actually makes a particular power supply. Also, if the UL logo is on the same label as the specs, you can be pretty sure that the UL listing pertains to the specs on that very label. Can you believe that there are a few companies that claim UL listing, but don’t put the logo on their label? That’s because the specs on that label are not the specs given to UL. And it’s a regular Easter egg hunt trying to figure out what the actual specs are using the UL number. So why bother? If the company can’t put a UL logo on the same label as the specs, they have something to hide and not worth doing business with.

Another way to classify the quality of a power supply is just from its weight. Simply put, a good power supply has good components in it. A better power supply has larger caps, transformers, heatsinks and overall more components than a cheaper unit. All of this adds up to more weight.

Also keep in mind the “get what you pay for� adage. It doesn’t always apply from brand to brand, especially if people take into consideration USEFUL improvements like modular cables, active PFC, etc. all add to the cost of a power supply. But when you see a power supply with a bunch of lights and other pretty things, you have to take into consideration that this added bling isn’t free.

Watts don’t mean squat! Know how to read the label!

I hope by now that you all know that Amps multiplied by Voltage equals Watts. And since a power supply for a computer puts out multiple voltages, the statement of how many total watts this unit puts out is really subjective.

The wattage rating is on the box of a power supply (like "Billtronic's 500W Mega-kleen-power") is the total capability of ALL of a power supply's rails COMBINED. The 5V, 12V, 3.3V, -12V, -5V and 5VSB capability are all added up to calculate a power supply’s “total wattage rating.� That total number really tells you nothing about the power supply's actual capability as it pertains to your particular PC.

First you have to ask, "is that wattage continuous power or maximum peak power?" Some power supplies will give you output ratings based on what the power supply can continuously output, while others give you peak power. For you audiophiles, this is similar to the difference between RMS and Peak. Some companies will actually rate a power supply at what it can continuously put out, but with a tolerance of 10% +/- from actual spec (12V, 5V, etc.)! Intel’s ATX specification for power supplies only actually allows for a 5% tolerance!

There are also variables that come into play like “what was the temperature at which the testing was performed?� “For what period of time was the testing performed at the specified wattage?� Basically, you should look at the amperage each rail is capable of and then just consider that the power supply's BEST CASE SCENARIO capability.

The first thing you can do is to try to figure out your computer's WORST CASE SCENARIO load. There are several calculators on-line that allow you to "add up" your computer's power. Unfortunately, the bulk of these give you a final calculation in wattage. But if you can figure out what your +12V load needs to be, which is going to be the bulk of the wattage of a modern PC, by adding up your drive motors, fan motors, lights, pumps, video cards and CPU's, and add them all up, you'll be pretty close to figuring out what your PC needs.

You’ll soon enough figure out how important the way the manufacturer distributes power across the rails really is. If you have a 500W power supply with 40A available on the 5V line and you're using a Prescott with SLI video cards, you might be in trouble because the 5V line alone is using up 200W of that power supply's total power not leaving much else for other rails! Given that most power supplies give you 20 to 30A on the 3.3V (which is way high by today's standards, but even 30A on the 3.3V is only 100W) and split up about 20W for negative voltage and stand by, you're only left with 180W for the 12V rail. That's only 15A! Mind you, we're talking maximum combined peak power, but better safe than sorry, right?

If you don't have the time or resources to do this, then just do this instead: Try to figure out if your PC is going to be 5V heavy or 12V heavy, and then buy the biggest, best quality power supply you can afford with the load balanced most appropriately for your PC. For example: If you have a Pentium III or an Athlon XP board without an ATX12V connector (like Biostar Socket A motherboards never have the 2x2 connector) then something with a relatively high 5V is most suitable for you. If you have a Prescott or an AMD64, consider something with a high 12V rail or rails (combined wattage) like a Silverstone ST56ZF or an OCZ 520ADJSLI. If you have PCI Express video card or cards, consider something with a really, really high 12V rail or rails (combined wattage,) like one of the SLi approved power supplies on nVidia's website.

So now back to helping you guys and gals read a PSU label. Use this as a reference:



This one is very simple. This power supply gives us 30A on the +3.3V rail and 30A on the +5V rail. Underneath these two, you’ll see where the maximum combined capability of these two rails is 150W. That means, you can load up the +3.3V to 30A by itself, and you can load the +5V rail up to 30A by itself, but you can’t load them both up to their maximum simultaneously. The rails are not additive. You’ll also see 0.5A on the –12V and 2A on the +5VSB. I’ll get back to the 12V rails in a minute.

Note that the total power of this particular power supply is 460W.

Ok… Now look at the 12V rails. There’s two 12V rails (I’ll explain why later) and they are rated at 18A each. The maximum combined wattage of those two rails is 32A.

What?!? But 18A plus 18A is 36A? Like the +3.3V and +5V rails I just mentioned, +12V rails are not additive. You can load each one up to 18A, but you can’t load them both up to 18A.

Now let’s go back to the “watts don’t mean squat� phrase. I don’t want to slam any brands, but take a look around at some 500W and 600W units. You’ll actually find that even though they may have more “total wattage� than this particular unit, this unit actually has more USABLE power on the 12V rails. Pretty interesting, right?

[dmelsie]

bag o pa pod ko dri nag pa member sa istorya ayos man d i pod dri we learn more from peps in here thnx sa addition sa ako post
ayos unta pod if under sa computer hardware nay sub folder dedecated for OC modding and general discussion about hardware para dili ta mag lisod pangita topics dba... naa ta pod ko mga mods i post dri pero and modding section sak sak sinagol man pero naa ko e try post testing lang gud simple guide sa pag mode sa side window... nya naa pod ko mode for psu unit pero mka void sa warranty lang nun pod.... hehehehe

[rexdudev75]

Wow! Thanks for the info bro! That is truly useful...