how i can identify a good PSU

[Astennu]

I made this topic because i want to know how i can identify a good PSU. I’m looking for a New Future Proof PSU. That had 8P VGA connectors. My Old Coolermaster Realpower 550 Watt. Had some problems and now I have a Corsair to test if the Coolermaster was the problem. And It was. The system is rock solid now.

 

I have seen some topic @ this and other forums and i don’t get some things I read:

 

1: ARE MULTIPLE 12-VOLT RAILS BETTER THAN A SINGLE 12-VOLT RAIL?

 

Quote From PCP&C:

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.

 

Most PSU makers have multiple 12v rails. Corsair Says:

Triple 12V Rails provide independent reliable power to the CPU, video card and other components with a combined rating of 50A (40A on 520W) maximum! Advanced circuitry design that automatically enables power sharing between the triple +12V rails in an event of overload on any single +12V rail.

 

So if there is a lot of power needed the lines will be linked. If that’s true multiple lines are no problem anymore. But is this true ? Does it realy work like that ? And do most PSU makers use that principle ? And What are the Con's ? Why Is a Top1 PSU builder using a single super Heavy 12v Line and others try to link separate lines ?

 

2: What power can my PSU realy Suppy to my System ?

 

 

620 VS 520 Watt both have 3x 12v @ 18a Max. But what is the continues output of theses 12v rails ? Corsair is talking about a combined power of 50A thats 600 Watt. And the PSU is only 620. If I Add the + 3.3 and the +5v I have 830 Watt of power according to the charts. I think that’s a lot. Even if its peak power. And how can the 520 Watt PSU have the same amount of peak power ?

 

And what are the bad things about the Coolermaster Realpower Pro PSU's of 850 and 1000 watt ? They are rated @ 6x18A Max output. The Corsair i have now has 3x18A Max. But the 850 watt coolermaster only has 230 watt more and 3 more 12v lines. + 12vx18A=216 Watt per line 216x6= 1296 Max for the 12v only.

 

Same With the P&C 750 Watt. It has 60a 12v raild thats 60x12= 720 Watt for the 12v rail only. I think thats a peak value. But i dont think that coolermaster 850 can peak 1300 watt on the 12v only.

 

So how should we look at these values ? Are they right ? And if a PSU can supply 18A and a other brand has 16A is it possible the 16A supply is more stable ?

 

I hope you guy’s can explain what these numbers mean. Sorry For my Bad English

[Astennu]

Some Extra Info On Point 1:

 

Quote From Sluggo:

Many folks wonder about "single-rail", "dual-rail", "triple-rail" supplies and which is better or more appropriate for what they plan to do with their machine. I just wanted to clear up what seems to be a common misconception, which is that these rails are independent of one another. In fact, with the exception of one family of supplies (that I know of), there is only one +12 rail in every ATX supply on the market. All the "rails" labeled on the power supply case are actually the same current source and labeled as separate rails only to comply with a UL requirement for consumer-class supply cabling.

 

Every ATX supply (with the one exception) has a single winding on the secondary of the main transformer that generates the +12 voltage. The output of this transformer is filtered and fed to all the +12 circuits in the PC. There are no other isolation or protection devices that would constitute a separate "rail", and all of the +12 lines in the PC go back to a single point in the PSU.

 

The one exception that I know of to this is the new Enermax Galaxy line, which starts at 850W for around $300. It has two separate secondary transformers for +12 and has separate output specs for each.

 

To sum up, the only number that really counts w/r/t +12V is the total +12 current available from the supply. All the "multiple-rail" designs you see are just a single +12 supply with one point of regulation and protection. I hate to see people get all wrapped around the axle on this one issue, which really shouldn't be an issue at all.

 

 

And another quote from Readbeard:

DISCLAIMER: I'm not an engineer, and I'll clear this by our engineers to see if there are any glaring errors here, but this is how I understand it.

 

The thing is, nobody makes a PSU with truly electrical independent +12V rails, as far as I know. The only difference between "single rail" and "multiple rail" PSUs is the OCP point. Once your multi-rail PSU's rail hits the OCP point, it's supposed to turn off as a safety feature.

 

The older ATX spec required that OCP point be no higher than 18A on each rail. As a result, Corsair (and other manufacturers) limited themselves to that in their specs. However, when the ATX 2.4 spec came out, they removed that limitation due to its inability to run higher-end GPUs, and Corsair (and possibly other manufacturers) raised the actual OCP.

 

So while our PSU is rated at 3 rails with an OCP of 18A on each, the true OCP on any given rail is considerably higher. A lot higher.

 

So why even have multiple rails? It was part of the ATX spec. The concern was that when a CPU and GPU are on the same rail, they'd overload the safety measures of the internal wiring. For those of you familiar with electronics, that's the only real risk. Wires and cables from the PSU are usually 18AWG or 22AWG. A PCI-Express 6-pin connector has 3 +12V and 3 Ground wires. There's a certain safety precaution to drawing too much power over those 3 wires, due to resistance. Is it possible to draw 30A on those wires? Sure. Is it possible to draw 60A on those wires? Sure. The only difference is, at some point, that wire's going to heat up due to the resistance, and cause a safety concern.

 

Since a lot of PSUs run the wires together to one connection point on the PSU's PCB, that connection point becomes a point of resistance, and thus when you draw too much power over that single connection point (usually a bunch of wires soldered to a 2cm x 2cm section of PCB) that area can heat up and cause safety concerns as well.

 

Which is one of the reasons why "multi-rail" PSUs exist. They typically have the wires spread out to decrease the overall resistance. It's not that big a deal to have a single rail for a PSU that can do, say, 400 watts. But when you start getting up in the higher wattage areas, you're going to want something that either has multiple rails or a physical separation of the connection points on the PCB.

 

We could have easily spec'd the HX620 to have one +12V rail @ 50A. It's true, in a way, since there's only one +12V source. But by that rationale, everyone with a multi-rail PSU could do that.

 

So all the debate over single-rail and multi-rail PSUs is really kind of pointless, since effectively, we're talking about a very small difference in design, and that difference is the Over Current Protection point. If you set the OCP on each physical connection at the total amperage possible of the PSU, you've got a single-rail PSU. If you set the OCP on each physical connection to something lower for safety precautions, you've got a multi-rail PSU.

 

This is my understanding of the technology, and while I don't have 20+ years in the industry like Doug, (as I would have been very uninterested in Power Supplies before I was 10 years old) I think it's mostly on the ball.

[Astennu]

And A nice 3e and 4e question With a quote From PCP&C:

 

3. DON'T LOSE POWER WITH MODULAR PLUGS

Due to their look, convenience, and cost savings for manufacturers, modular plugs have become a popular power supply feature. Unfortunately, there has been little or no discussion of the impact of this feature on overall performance and reliability. The fact is, modular plugs limit power by adding to electrical resistance. The voltage drop can be as much as would occur in 2 feet of standard wire. Worse yet, modular plugs utilize delicate pins that can easily loosen, corrode, and burn, creating the potential for a major system failure. That's why professional system builders specify uninterrupted wire!

 

True or false ?

 

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.

 

I cant really Awnser these questions But i think some of you have more knowledge about these things.

[Yellowbeard]

And A nice 3e and 4e question With a quote From PCP&C:

 

 

 

True or false ?

 

 

 

I cant really Awnser these questions But i think some of you have more knowledge about these things.

 

Think about this. EVERY power plug on a PC PSU is a MOLEX plug of some sort on one end. If this was an inferior design, the problems hinted at by PC P&C would occur on every power supply as they all have plastic plugs and connectors on one end of the harness. Therefore, a properly implemented modular design uses proven technology, it simply uses it on both ends of the harness instead of 1. There's nothing wrong with modular. Both methods are fine.

 

Our PSUs can output their rated power at 50c cooled with a 120mm fan cooling it. It works just fine.

 

Just because PC P&C chooses not to use certain ideas or design features, it does not mean these are bad ideas. PC P&C makes great PSUs but, so do we. We simply choose to do some things differently from them to make our products great for our customers.

[davidhammock200]

Think about this. EVERY power plug on a PC PSU is a MOLEX plug of some sort on one end. If this was an inferior design, the problems hinted at by PC P&C would occur on every power supply as they all have plastic plugs and connectors on one end of the harness. Therefore, a properly implemented modular design uses proven technology, it simply uses it on both ends of the harness instead of 1. There's nothing wrong with modular. Both methods are fine.

 

Our PSUs can output their rated power at 50c cooled with a 120mm fan cooling it. It works just fine.

 

Just because PC P&C chooses not to use certain ideas or design features, it does not mean these are bad ideas. PC P&C makes great PSUs but, so do we. We simply choose to do some things differently from them to make our products great for our customers.

I have personally tested many PC P&C PSU's & they were excellent,

however the Corsair 620W is the finest PSU I have ever tested, damn near perfect in every way!

 

The Corsair 520W, which I have also tested is an excellent PSU below the uber SLI/CF level.

 

I highly recomment the Corsair 620W for up to 8800GTS SLI,

for 8800GTX SLI I recommend the PC P&C 750W Quad.

 

Good Luck,

Dave :angel:

[Yellowbeard]

Thanks David, I am glad to see that you like our PSUs and we appreciate your endorsement. Old Fart Overclockers know best ;-)

[davidhammock200]

Thanks David, I am glad to see that you like our PSUs and we appreciate your endorsement. Old Fart Overclockers know best ;-)

Your people sent me the PSU's for testing &

I couldn't find find any "actual, real PC" in all of Las Vegas that it couldn't power!

 

Although the 520W is an excellent PSU, it is so close in price ($96 vs $127)

that the 620W has to be the primary recommendation in the 8800/R600 GPU era.

 

Keep up the good work!

Dave :angel:

 

PS: Please send me the new 800+ & let's see how it handels the R600's in CrossFire.

[Astennu]

I would love to see a 800+ Watt version with PCI-E 2.0 Connectors Thats the reason i'm gonna return the HX620 i have atm. Because i will buy one for two of these cards so my new PSU will need the 8P connectors.

[Praz]

If you are getting two R600 cards you should be looking at the rest of your system. In it's current state, one card will not be able to reach it's full potential much less two.

[Astennu]

If you are getting two R600 cards you should be looking at the rest of your system. In it's current state, one card will not be able to reach it's full potential much less two.

 

I know. I will start with one. And later this year i will buy the new K10 Quad core. But that one is not available until Q3 ( for us normal users and tweakers ) Server version will be released in Q2.

 

But i don't want to buy a new PSU every year. I want to keep it 2-3 years. My realpower 550 watt is only 15 months old. And already useless for a not even super high end setup. So i want to get i right this time. And for the full R600 experience you will still need that 8P VGA connector.

[custom_coms]

Chances are you won't "get it right," unless you go ALL OUT and get the latest 1000 watt psu's from Tagan, PC P&C, and OCZ (not sure if the OCZ ones are to market yet?). Anyway, the graphics card companies (Nvidia and AMD/ATI) keep increasing power on the uber-high-end with each generation of card released. Thus, you need a new psu. I can't think of a time when PSU requirements increased this fast, and the requirements are being driven by the GPU primarily-you think dell is sticking 500+ watt psu's in their low-end C2D systems? How to avoid this? Don't buy the latest high-end gpu's and then pair them in SLI/Crossfire. Stick with one high-end or even a mid-range card. On the other hand, if you have the money for SLI/Crossfire every 12-18months, a new psu at the same time isn't expensive compared with the overall system cost.

[Kingfisher]

Why spend money on those new cards? The ones out now are more than plenty, wait a while there is no need for these rediculous cards because the games don't need them, at least not for anytime soon.

Just like when the 8800gtx came out, folks tossed down 7 bills for it and in less than a year later it dropped quite a bit. It still is overkill for the average gamer.