Raidmax RX-520XP PSU Author: jonnyguru Date Posted:17/03/2005 10:07.18 SLRating: Bottom Line: There's more to picking a PSU than the wattage, as explained in the first of a series of forthcoming PSU reviews. Article Navigation Introduction Wattage Parameters Methodology RX-520XP Observations Overview Results/Conclusion Pages: 1 2 3 4 5 6 7 8 Discuss This Article

Methodology

Everything I need is all laid out on my dining room table.  Thanks to Ultra Products for the big ol' anti-staic mat.

The SunMoon SM-268 can dynamically load a power supply at the push of a button. There's five memory settings and the ability to crank up the amperage while the power supply is already up, running and loaded. I have three memory settings set to settings that can perform the above three tests. The other two tests are set up for dual 12V rail power supplies and I'll explain those later.

In the lower left of the SM-268 is a cluster of power connectors I plug the power supply into and a toggle switch that I toggle for single 12V rail and dual 12V rail power supplies. If I'm testing a dual 12V rail power supply, I make sure I plug the 2x2 12V connector into the SM-268 because that connector gets it's power from 12V2.

Here is where I set the amp load for each rail.

With the press of a button, I can test the output voltage of each rail while it's under load.

Some math is done for me. This mode of the tester shows me how much wattage is being put out on each rail, as well as the total wattage.

Along the bottom of the display of the SM-268 is a number of buttons. It's quite intimidating and sometimes to accomplish something you have to push a "shift" button and another button simultaneously. I have most of my settings pre-programmed, so all I have to do is select "memory 1," through to "memory 5." I then have an up and down arrow for increasing and decreasing load while the tester is running. I use these arrow buttons for bringing the juice down for my zero load test and cranking my juice up to see where the limits of a particular power supply may be.

For the record (because someone asked me this the other day,) the preset loads that I have pre-programmed into the SM-268's memory DO NOT ramp up. The load on the PSU is immediate, so not only does the Power Good signal on the power supply have to work correctly, but the power supply also has to be able to accept a sudden, nearly crushing load, in a split second's notice. The only tests that are "ramped" is the zero load (where I ramp down from test two) and the full load (where I ramp up from test three.)

I have a Compu-Nurse plugged in as well so I could see what operating temperatures are. I began doing this after loading up an Antec and Enermax power supply and noticing how hot the air coming out of them were. I also shut down an Ultra PSU abruptly after a 550W load and noticed the housing getting very hot.

Busting out the old school calculator and notepad for this test.

The only thing I'm missing is a Waveform Monitor, which I think I can get off of eBay for about $100, but that's one more thing I'll need to learn how to use and right now I just want to get started with testing power supplies using the methodology I have already determined that I will use.

So without the waveform monitor, I won't be able to test the cleanliness of the rail.  This is a shame, as it's very important that a rail is not only powerful and within spec, but that it has little ripple.

There's also a few things that I KNOW I won't touch on, so let's get those out of the way so I can minimize the hate-mail now instead of down the road.....

What I'm not going to touch on

As I said, I don't have a waveform monitor so I can't test how "clean" a rail is, but it is obvious to me when a power supply's DC voltage becomes unstable because the voltage will fluctuate wildly.  Fortunately, this coincides with the voltage being out of spec (5% on the positive DC voltages and 10% on the negative DC voltages) so it's pretty easy to guesstimate the limitations of a particular power supply unit.

I'm also afraid I will not report on noise.  SilentPCReview does a GREAT job on testing power supplies for noise.  You want to check them out.  If a power supply is really quiet, I'll state it. If a power supply is really loud, I'll state that too.  But I'm not going to report noise levels in decibels, etc.  To effectively test a power supply for noise, one needs to either install the power supply into a system or have a test rig designed for the task.  One also needs to have access to an accurate sound meter.  I do not. SilentPCReview does.

I do only touch on the subject of power supply temperature.  As it is, the act of pulling out the CompuNurse was an afterthought because of observations I made regarding temperatures.  Again, this is not done to any scientific detail because I'm testing power supplies outside of a case.  A wild guess would be to say that any power supply I test will actually run hotter inside a PC than it is on my table.  This is because it's not drawing in outside air when installed into a case.  A power supply usually sucks hot ambient air in from the inside of the case because a power supply really is a part of a PC's total cooling solution.

Speaking of temperatures; I know I'm going to get some people pointing out to me that the efficiency, or even the capability of a power supply to produce it's maximum rated wattage, decreases as it's temperatures increase.  For this I will respond with... "And?"  This is an issue with most review sites that merely throw a power supply into a case and fire it up and judge it based on how well it ran in their system.  Let's say the room temperature is 25°C.  This is the same temperature that power supplies are usually tested at (there's a few exceptions.)  Let's say the ambient temperature in the case is 35°C (a little warm, but what the heck!)  Naturally, the ambient temperature of a case is going to raise the operating temperature of the power supply immediately making the power supply's "rating" inaccurate.  So when a review site tests a 500W power supply in a hot case, they may only put about a 300W load on it tops, never realizing that due to the rise in operating temperature the maximum capability of that power supply may only be 400W (using REALLY round numbers here.)  So how am I any different?  Well, I admit that I'm working in a 25°C environment outside of a case.  But as the power supply puts out higher wattage, it generates it's own heat (which of course varies from power supply to power supply) thus increasing it's operating temperature, thus decreasing it's capabilities.  Despite this, I'm still putting the same load on the power supply.  500W is 500W.  20A on the 12V rail is 20A.  One has to take in consideration that I am putting long term worst case scenario loads on the power supplies, so if it can do it's rated wattage at whatever temperature it happens to be running at for the length of time I run it at (usually an hour) then I think my point has been made.

That leads me to how OTHER SITES with load testing equipment test their power supplies.  I say:  "Label be damned!"  Fact of the matter is, the means that companies get the results they put on their labels vary wildly.  I'm not playing that game.  Typically, a review site will load up each rail based on what the label says.  The guy who showed me how to use the SunMoon did the same thing.  I immediately said, wait a minute... I buy a power supply to suit my system.  I don't build my system up to suit my power supply.  Why would I load test a power supply based on what I think it can do based on it's label?  I should load test it based on what a REAL PC would load it up at in a worst case scenario.

With my Raidmax review, you'll see that I find that the power supply, despite being "rated" at 18A on the 12V rail, ran at 20A.  I was able to obtain 20A on the 12V and 20A on the 5V and maintain stable power.  I was only able to get 469W out of the power supply without causing the overload protection to trip.  This means the power supply is NOT capable of it's label rating.  Although this is a sort of "false advertising" I'm not going to drag the power supply in the mud and state that it's crap because of it.  If I had a machine that was similar to one of my simulations that the power supply passed, I would have no reservations using said power supply.  So the Raidmax 520W is actually a 465W.  So they're trying to lie to customers by claiming it's a 520W.  That doesn't mean it's not a good 465W!  :-)

And now... ON TO THE POWER SUPPLY TESTING!

1. Raidmax RX-520XP PSU
2. Ultra X-Connect 500W Titanium PSU
3. Ultra X-Finity 500W Power Supply
4. Ultra X-Finity 600W PSU
5. Powmax Demon 580W PSU
6. PC Power and Cooling Turbo-Cool 510 Express
7. Fortron-Source FSP530-60GNA
8. Thermaltake W0021 Purepower Butterfly 480W PSU
9. A.C. Ryan Ryanpower2 CableFREE 550W ACR-PS2100
10. Mad Dog Multimedia MD500-SCPS
11. OCZ ModStream 520W
12. Thermaltake Purepower TWV480 PSU
13. ePower PCMCIS Fanless 450 LION
14. TTGI SuperFlower Plug-N Power 550W
15. OCZ PowerStream 520ADJ Power Supply
16. Silverstone Zeus ST65ZF Power Supply

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