Anandtech to Review Power Supplies

PSUs: The source of DC power for all components in the PC & often a big noise source.

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gforcefan
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Anandtech to Review Power Supplies

Post by gforcefan » Thu Jul 12, 2007 8:18 am

There is a long article about the methodology they will use.

Here is a link to the portion of the article regarding how they will test/evaluate fan speed and noise.

http://www.anandtech.com/casecoolingpsu ... i=3021&p=7

A big thanks to SPCR because a couple of years ago big sites ignored silent computing and now they all have taken notice.

continuum
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Post by continuum » Thu Jul 12, 2007 9:29 am

Looks pretty good. I like how they emphasize their additional precision. It's a nice but ultimately more for bragging rights than any real utility to the average enthusiast.

I am curious to see what their PSU test lab noise floor and whatnot turn out ot be, tho. :)

HardOCP, Anandtech... nice to see 'em! :)

MikeC
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Post by MikeC » Thu Jul 12, 2007 9:51 am

This looks like a decent effort but as usual, the thermal and acoustic aspects of the testing are flawed.

1) A 1 meter cube box is a horrific acoustic test environment. It's way too small to avoid boundary effects. All the stuffing in the world will not help. You can see in the photo that the mic has to be at one corner and the PSU in the other corner to have 1m distance. Ever stand in the corner to sing? Notice what happens to your voice?

The box will impose its very significant acoustic signature on everything they measure or record in there. The most important effect will be boosts in all the freq below ~500Hz, along with peaks in certain bass frequencies. Any fan used in any PSU will excite such resonances.

Also, there's no indication of what ambient noise level they're getting in there with the Chroma testers going. They mentioned 15 dBA -- I say no way with the Chroma machines going. I actually bought a similar AC source device a few years ago and had to abandon it due to the noise problem -- it easily reached 60 dBA @1m. For their test box to achieve 15 dBA ambient with the Chroma machines going in the same room, the box would have to have something like >35 dBA noise isolation and/or the room would have to be gigantic. The former requires astonishing acoustic technology and knowhow, the latter is unlikely.

2) The PSU will be in the 1m test box more or less by itself. The box will be sealed during testing. This is unrealistic for 2 reasons -- A) a PSU in a real PC always see some fresh air intake, and B) it also sees at least some of the heat produced by the components it is feeding. So thermally, their test environment is nothing like a real PC.

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Post by Das_Saunamies » Thu Jul 12, 2007 10:19 am

Do I hear a list of suggestions for Anandtech forming...? :wink:

continuum
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Post by continuum » Thu Jul 12, 2007 10:47 am

Yes, you do. They mentioned thermal stress in their thing, which a sealed 1m box would do quite nicely.

Not realistic at all, but their emphasis on precision is amusing. :)

gforcefan
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Post by gforcefan » Thu Jul 12, 2007 11:03 am

Thanks Mike. I learn a lot reading the articles and posts here - that is why I am always lurking. It will be interesting to see their results once they test a few psu's (especially if they review units that were also reviewed here).

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Post by dhanson865 » Thu Jul 12, 2007 6:57 pm

MikeC wrote:This looks like a decent effort but as usual, the thermal and acoustic aspects of the testing are flawed.
They also didn't mention the decibel meter they are using. If it is their old unit it doesn't have any accuracy below 36 db(A).

Or are they using that amplifier to turn a 20 db(A) sound into 40db(A) and trying to divide by 2?

mcoleg
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Post by mcoleg » Thu Jul 12, 2007 8:29 pm

the part about temperatures worries me a bit:

http://www.anandtech.com/casecoolingpsu ... i=3021&p=6

they assume 25C is the ambient psu's are rated at. shows that they didn't dig dip enough.

OCC_Yoda
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Post by OCC_Yoda » Thu Jul 12, 2007 11:21 pm

mcoleg wrote:the part about temperatures worries me a bit:

http://www.anandtech.com/casecoolingpsu ... i=3021&p=6

they assume 25C is the ambient psu's are rated at. shows that they didn't dig dip enough.
As usual ya didn`t read what was said....and you didn`t think through your response...

Temperature

"The ambient temperature around the power supply will constantly grow with the time of the test. It will be placed in the same set of conditions it will experience in a real system, where the temperature rises over time. We will start at a room temperature of 77°F (25°C) and constantly measure the exhaust temperature of the power supply and the installed heatsinks inside the PSU. This will tell us how well the power supply can dissipate the produced heat."

All the above is true.....
Since anand`s is NOt SPCR lets be a little pro-active and say that although a quiet PSU is a good thing..

Just because a PSU is a quiet PSU does not means it is also a good quality PSU!!!
Quiet does not equate quality......
albeit a quality PSU can also be quiet!!

Peace!!

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Post by MikeC » Fri Jul 13, 2007 12:03 am

It will be placed in the same set of conditions it will experience in a real system, where the temperature rises over time.
While the temperature will rise over time simply because the sound box will be closed when the PSU is being tested, it is definitely NOT the same set of conditions as in a real system.

As mentioned in my earlier post, in a real system, the DC output of the PSU goes to components that heat up. These components are in the same case as the PSU, and they affect the ambient temperature of the PSU. Case fans obviously affect the overall thermal situation for the PSU, but the PSU's cooling fan draws air from inside the case. Unless the PSU is in a separate chamber with its own intake vent, it has to deal with not only the heat generated within itself as a result of AC/DC conversion losses, but also at least some of the heat from the components it powers. Heat can affect a PSU's max power output capacity, its stability, and of course, its fan's speed/noise.

It's because Anandtech is trying to do "serious" acoustic testing that all this becomes important. In SPCR's PSU testing, we have a very clear operational model: The test rig is a close facsimile of a quiet enthusiast's low airflow, low airflow-impedance system. Anandtech's test setup doesn't resemble any real system -- there is no fresh air intake, and the exhaust heat goes nowhere. Can such a test setup tell anything practical and worthwhile about the noise/load or the heat/load behavior of any PSU? Certainly not if you intend to install that PSU in a case where there are case fans, intake vents, and other components that also get hot.

It seems to me that in their setup, once a certain amount of heat has been generated inside, continued testing can only lead to continually rising temperature for any PSU. In other words, the temperature/load relationship will be dictated almost entirely by how long the PSU is kept running. The heat is trapped in the box; it has nowhere to go, and the box is very well insulated. Even at a modest 100W load, leave it running in that test box for a few hours, and I'd bet $$ almost any PSU will shut down due to overheating. So where in the rising curve (over time) could you say is the right point to look at temperature or fan speed or noise? This is a challenging problem.

This is completely different from SPCR's test rig. We generally try to do all the PSU testing at the same room temperature (20~22C), which we can maintain most of the year -- we don't do PSU testing on hot July and August days. This does not stop the internal temperature of the test rig from reaching upwards of 50C at high power load. Importantly, at almost any load level with almost any PSU, the system does come to an equilibrium where temperature (in and out), fan speed and noise stabilize. This is then the obvious point to stop and take measurements.

Furthermore, in the SPCR test rig, almost any well-built PSU can be run at ~75% of rated power indefinitely without overheating. I wanted to say 100%, but I suspect this is not true -- even some of the well-built PSUs may overheat at full load if left in that state long enough. All this is to say that our test rig has predictable thermal characteristics that do resemble a real PC system, which is very important if you want to do accurate acoustic testing / analysis. It's also important for thermal analysis.
Last edited by MikeC on Fri Jul 13, 2007 12:30 am, edited 2 times in total.

mcoleg
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Post by mcoleg » Fri Jul 13, 2007 12:23 am

OCC_Yoda - i thank you for your kind observation.

i was referring to the last paragraph on the page:

"normal power supplies are all rated just at room temperature of 77°F (25°C)."

if you need more explanation on the topic, please ask someone who cares.

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Post by Aleksi » Fri Jul 13, 2007 6:30 am

The Chroma equipment is good, I've used them in functional testing setups in production facilities with various products.

MikeC, the load is definately a noise maker. I think it has 2-3 high speed 120mm fans. Can't remember what the cooling setup is in that AC source. Anyway, they will most likely affect the noise measurements, atleast in their "15dB(A) environment".

It would be interesting to see the wiring diagrams for the measurements, load wiring etc.

It would be nice to see an additional DAQ / Scope card (PCI, obviously not PXI) in there. Lots of possibilities for automated tests, response times etc etc with small additional money if they only had the SW skills (LabVIEW or CVI). Hmmm... maybe I'm getting a bit carried away :lol:

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Post by burebista » Fri Jul 13, 2007 12:43 pm


dhanson865
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Post by dhanson865 » Fri Jul 13, 2007 7:24 pm

wow, that review was a stinking pile.

If they aren't going to vent heat automatically at least allow the unit to cool to room temp before testing a 2nd time. As is the 115v tests are artificially worsened compared to the 230v tests.

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Post by NeilBlanchard » Fri Jul 13, 2007 7:28 pm

Hello,

http://www.anandtech.com/casecoolingpsu ... =3037&p=15

The chroma is in another room, from the PSU being tested.

1000RPM fan is 26dBA?

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Post by MikeC » Fri Jul 13, 2007 8:59 pm

NeilBlanchard wrote:Hello,

http://www.anandtech.com/casecoolingpsu ... =3037&p=15

The chroma is in another room, from the PSU being tested.

1000RPM fan is 26dBA?
I don't think so. The other room is that 1m cube box.

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Post by continuum » Fri Jul 13, 2007 9:05 pm

dhanson865 wrote:If they aren't going to vent heat automatically at least allow the unit to cool to room temp before testing a 2nd time. As is the 115v tests are artificially worsened compared to the 230v tests.
No kiddin'.

I expect them to have a pile of dead cheapo PSU's once they start testing those...

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Post by MikeC » Sat Jul 14, 2007 6:19 am

All the output lines sagged badly as load was increased, which JohnnyGuru conjectured was due to the losses in the cabling between testers and the PSU. I think it may also have to do with the extreme heat in the box?

I would ask how long the PSU was run at each load level (and in total) and what was the air temperature at the PSU intake? Maybe the test box is just letting the PSU get way too unnaturally hot, and this has a deleterious effect on performance. This test box is not the same as thermal control chamber where you can dial in a specific target temperature, which will then be held constant by the chamber throughout the testing.

Repeating myself.... Since the test box is well insulated and sealed, there is a direct correlation between time spent with the PSU on and internal air temperature. No matter how the PSU is cooled, at any load, the temperature of the test box should rise continuously (even if only incrementally at very low load) as long as the PSU is running. This is a significant uncontrolled and unreported factor. That PSU intake temperature will be dictated by a complex mix of factors, by too many variables --

-starting ambient air temp in the box
-how long the PSU is kept running in the box and at which loads
-heat loss out of the box
-efficiency curve of the PSU
-fan and fan controller characteristics

If the time spent at each load and the starting ambient temp is kept the same for each and all PSUs, then the variables are correctly contained to the PSUs being tested. Then differences in the air temperature at the intake at any given power level for each PSU would reflect real differences in the cooling system and efficiency of each PSU. It would ensure a more level thermal playing field.

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Post by burebista » Sat Jul 14, 2007 9:10 am

Kudos to AnandTech for their effort, but I have doubts about results.
Something it's not OK there, and no ripple measurements.
We have jonny's Olympia 650 review (which is a Decathlon non-modular) and I don't see 3.3V and 5V out of specs and exhaust temperatures were lower in jonny's review.

For now I'll stick with jonny and SPCR PSU reviews.

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Post by EsaT » Sun Jul 15, 2007 12:21 am

That box will mess acoustic and temperature measurements... and through temperature make anything else questionable.

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Post by mcoleg » Sun Jul 15, 2007 4:24 am

there are much more reliable ways to measure with different ambient, if that's the goal.

one could heat up the intake, for example. it's easy to control and easy to implement. even i manage to do that and i sux at testing :P

gforcefan
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Post by gforcefan » Sun Jul 15, 2007 2:01 pm

On the first page I knew it would be terrible when the author starts talking about a single rail versus multiple rails and Intel's design specs.

If you are doing a "review" for a large website, either find out the correct information, indicate that you will find out and update the article appropriately, or at the very least say nothing.

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Post by psiu » Tue Jul 17, 2007 1:13 am

Unfortunately, for the most part, their reviews have been basically useless for awhile. I could probably ask my wife to do reviews and she would be better at it. They basically rehash the press releases, use some shady methodology with absolutely no forethought or backwards comparisons (because every test platform is different) and more or less just fall in love with the blinking lights.

Their PSU test methodology sounds pretty similar...LOOK WE HAVE EXPENSIVE GADGETS...dunno what to do with them...BUT THEY BLINK A LOT AND HAVE KNOBS, YO!

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