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 Post subject: Estimating power i need for my system.
PostPosted: Mon Oct 25, 2004 9:12 am 
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I need new psu and i decided to count how much power i need so i build this chart but i dont know how much power motherboard alone will use and couple of other peripherals. There is no info in manual so I emailed to asus support and was told mobo alone will use 85W, but they did not know how much power it use on each rail so suggested me to email to technics but i got no replay from them :( can someone share this info with me, my mobo is ASUS P4G8X.
Also if something in my list looks terrible wrong tell me.

Edit updated table 31.10.2004:
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Last edited by z_unit on Sun Oct 31, 2004 8:26 am, edited 3 times in total.

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PostPosted: Mon Oct 25, 2004 9:18 am 
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Could you tell us what your CPU and Video card are? Number of drives and fan types might be nice, but they're typically not as significant.

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PostPosted: Mon Oct 25, 2004 9:44 am 
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Could you give us some background on where these amperage esitmates are from?


The 85watt total for the motherboard is total bunk. Not sure where they got that from, but it's nowhere close to reality. Maybe 5 watts total for the motherboard.

Your CPU is going to pull about 85 watts, max, not 120.

The 70watt for the VGA card is suspect as well, unless you're talking about one of the latest, hottest cards.

The wattages for the hard drives are about double what they should be, at spinup they might pull that much, but in normal operation they only use 13-15 watts. (at startup other things, like your VGA, aren't pulling much juice, so that compensates)

I wouldn't count the cdrw/dvd/floppy drives at all, since you never run them all at once. When they are running, it's virtually impossible for everything else in the system to be maxed out as well.


I would read through the How much will a 300w power supply run? thread and see just what sorts of systems people are running on "little" 300watt PSU's. You'll be surprised.

In reality, a good 350watt PSU is probably all you need.

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 Post subject:
PostPosted: Mon Oct 25, 2004 11:08 am 
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z_unit.....This article has some good words to say regarding power estimation, but you should take the numbers in it with a grain of salt, some of them seems to be a bit off. On this subject there are a lot of different opinions, I haven't really find any information that appears to be totally correct. That includes the different power calculators that you can find on the web.


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PostPosted: Mon Oct 25, 2004 9:30 pm 
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Actually i started from firingsquad.com numbers and changed them a bit to power specs i could find for hardware i use.
I get video (ATI 9800 XT) power consumption from this xbitlabs.com artcle.
My CPU is P4 2.4 GHz @ 2.7 GHz, but maybe i upgrade sometime so i would like to think cpu use 10A.
Let me update my table to show which power specs i know for sure for my hardware (green) and which i am not sure (gray).
I fillled max USB can use.
I am not sure should i include mouse and keyboard because they work from usb. And of course statement about motherboard is completely incorrect.
P.S. about 300W or 350W psu's, i want first count how much power i need and then pick psu.


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 Post subject:
PostPosted: Tue Oct 26, 2004 6:29 am 
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Rusty075 wrote:
Your CPU is going to pull about 85 watts, max, not 120.
ASUS USA TechSupport wrote:
The board alone will use about 85watts from your power supply. Thanks.
Dunno i guess they know better, but still dont have email saying how much will it use on each rail.

Rusty075 wrote:
The wattages for the hard drives are about double what they should be, at spinup they might pull that much, but in normal operation they only use 13-15 watts.

I get power for one of my hdd's here ( http://www.seagate.com/docs/pdf/datashe ... 7200.7.pdf ) and what you mean by spinup?

Rusty075 wrote:
I wouldn't count the cdrw/dvd/floppy drives at all, since you never run them all at once. When they are running, it's virtually impossible for everything else in the system to be maxed out as well.

What if i rip DVD to hard drive while playing PC game (not full install) and it reads needed files from cd-rom? So all my system is loaded. :wink:


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 Post subject:
PostPosted: Tue Oct 26, 2004 7:12 am 
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Don't take my word for it, take Intel's: they rate your CPU at 81.9 watts TPD. They under-report as a rule, so 85 is probably a safe estimate.

What the Asus tech support person may have been reading is what the board is rated to draw as a maximum, that would include the CPU.

There is simply no way that the board draws 85 watts all by itself...that's complete rubbish. My testbed has a CPU that I know draws 110 watts...the complete system draw from the PSU, at full load, is 137 watts. That includes a single HDD and a 9500Pro VGA.


HDD spinup: Think about driving your car. You have to press the gas harder when accelerating from a stop than you do once you're just maintaining the same speed, right? Same thing with you HDD's. The motor draws the most juice when it first starts spinning the platters, that the 2.8A max that the datasheet lists. That draw lasts less than a second. For the rest of the time it draws between the 12.5 and 7 watts listed below the max.




Ripping a DVD while playing a game still won't max everything out. You'll be IDE limited, and everything will stutter along rather slowly. (trust me, I've tried :lol: ) Besides, why worry about something that will never happen?

Read the thread I linked before: there's several examples of people in there who have done real empirical tests of what kinds of power their system actually draws. That information is a much better guide to go from than a manufacturer's Worst Case data, or dubious Tech Support information.

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 Post subject:
PostPosted: Tue Oct 26, 2004 8:05 am 
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Good advice from everyone so far. A practical approach: Get a good 400 watter. It will be more than enough for what you have and probably last you through a couple more upgrades. The price difference between a good 400 and lower power units is only $10-30... Don't sweat the fine power draw details, they are all estimates anyway. Most "tally-up-the-individual-power-ratings" make 2 assumptions:

1) that max power from each component can be drawn simultaneously by a PC. This is utterly impossible. About the only time you get even vaguely close is at turn on, and most decent PSUs will easily give you much higher than rated power for a couple seconds especially when cool (at startup).

2) that most PSUs are false rated -- ie, they don't really put out what they claim to do in real circumstance. This is generally true, but with the better brands most often recommended here, you can have faith that the output ratings are closer to reality than with a $28 500W Brand X. One very simple thing to look for the the max temp at which the PSU is rated. A 300W rated for operation at up to 50C is almost assuredly better than another rated for 400W at 25C. The latter at 50C will probably produce only half its rated power -- and 50C is much more likely in a PC than 25C.

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 Post subject:
PostPosted: Tue Oct 26, 2004 8:56 am 
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Rusty075 wrote:
Don't take my word for it, take Intel's: they rate your CPU at 81.9 watts TPD. They under-report as a rule, so 85 is probably a safe estimate.

I have not found specs for my cpu on intel site so i according to numbers from this article from firingsquad.com besides they say its from intel pdf's and its saying Northwood 2.4GHz uses ~8.5A. And 8.5A*12V=102W.
I would be grateful to you for link where Intel name different numbers.
Also i am not sure, but dont the cpu take more power when its overcloked?
So if i OC 2.4 to 2.7GHz should not i refer to 2.7GHz power consumption? Anyway i plan to upgrade cpu to 3GHz so 10A (120W) for CPU should be fair.


Rusty075 wrote:
There is simply no way that the board draws 85 watts all by itself...that's complete rubbish. My testbed has a CPU that I know draws 110 watts...the complete system draw from the PSU, at full load, is 137 watts. That includes a single HDD and a 9500Pro VGA.

I to doubt because of it so i working on getting more correct/detailed numbers.

MikeC i will bot buy no name or low branded PSU of course i can just buy 400W one and forget about it, but i want to go way i choose.


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 Post subject:
PostPosted: Tue Oct 26, 2004 9:22 am 
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z_unit wrote:
I have not found specs for my cpu on intel site so i according to numbers from this article from firingsquad.com besides they say its from intel pdf's and its saying Northwood 2.4GHz uses ~8.5A. And 8.5A*12V=102W.
I would be grateful to you for link where Intel name different numbers.
Also i am not sure, but dont the cpu take more power when its overcloked?

Here you go (Warning: It's a PDF file and an FTP link). Go to page #69.

By my readings, you draw 66.2W from your CPU. Granted that's typical usage and not worst case scenario. Maybe more if you plan on overclocking, but not all that much more.

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 Post subject:
PostPosted: Tue Oct 26, 2004 10:31 am 
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Here's the Holy Grail of CPU power information: Processor Electrical Specifications. Every CPU from the 286's to the Xeon's, and every manufacturer, all in one place. :lol: And much easier than digging through Intel's cluttered website.

Another good link: Benchtest.com's Overclocked Wattage Calculator From there, a 2.4 running at 3.0 will draw about 93 watts.

Those are two of my favorite sites for digging up CPU power information. Information on the other parts is harder to get, but for at least the CPU we've got a pretty understanding.



How much wattage the motherboard itself actually draws can really just be ignored. Once you take out the CPU, VGA, and HDD's, everything else amounts to just a couple of percentage.

All these numbers are guesses and averages anyway.... individual CPU's will vary by 10-15% or more...so there's no real need to get super precise.

But I understand and support your desire to know more about how much power your parts actually need. It's a good thing to be curious. :lol:

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 Post subject:
PostPosted: Tue Oct 26, 2004 1:09 pm 
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z_unit wrote:
I have not found specs for my cpu on intel site so i according to numbers from this article from firingsquad.com besides they say its from intel pdf's and its saying Northwood 2.4GHz uses ~8.5A. And 8.5A*12V=102W.


Well, finding out the actual power drawn by the processor when reading different numbers in different documents and webpages can really get you confused or maybe I'm just missing something. I've also had a hard time finding accurate specs, but in my case it is an AMD CPU (no pun intended).
According to the, widely available, electrical specifications for AMD Athlon and Duron processors the XP 2100+ Palomino draws 72W (41.1A@1.75Vcore). However, looking through the "Builders Guide for Desktop/Tower Systems" from AMD I saw an example on how to calculate the power consumption, the above mentioned processor is used in this example and it says the processor is drawing 89.91W (7.49A*12V). Now which number should I rely on?

I don't think this has any relevance in the matter, but I would like to mention what seems to be a curious coincidence.
AMD recommends that to find a suitable power supply wattage for a system only 80% of the total power drawn by the components, except for the CPU, should be taken into account. That sounds reasonable, what's curious however is that this is in accordance with the difference between the wattage numbers above, 72W is pretty much 80% of 89.91W and the same holds true for the XP 1800+ Palomino (also used as an example in the builders guide), the wattage numbers for that CPU is 66W and 82.47W.


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 Post subject:
PostPosted: Fri Oct 29, 2004 9:37 pm 
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Updated table, but i leave cpu on 10 :P.
Ok i think i will be just fine with 420 W psu with adequate amperage on each rail, but i dont want it to work at the breaking point so i go with something like 470. Well now i go pick some usable psus.


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 Post subject:
PostPosted: Sat Oct 30, 2004 4:36 am 
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Ok here is list of psu i could possibily buy. Now i go into studying each of them. If you have any comments or recomendations please post.

Image


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 Post subject:
PostPosted: Sat Oct 30, 2004 7:57 am 
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Suggestion:

1) Buy all your parts except the PSU
2) Buy a Seasonic Power Angel AC power meter (~$30)
3) Assemble everything
4) Use your old PSU or borrow one to connect your components. It would be best if you use one SPCR has tested so we can know exactly what its efficiency is.
5) Use the Power Angel to measure the POWER (W) being drawn at startup, idle, general use, and a max use -- whatever load you can throw at it. Just look for the highest numbers you can see on the Power Angel LCD screen.
6) Now come back and report your findings.
7) I will be able to tell you exactly how much DC power the system is drawing from your PSU (if it is a SPCR tested PSU). From this info, you can make a very informed PSU buying choice.

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 Post subject:
PostPosted: Sat Oct 30, 2004 9:39 am 
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Cant, i am from Europe and it dont supports 220VAC.
Anyway i cant get psu just for try out here, but its curious to me how much power my pc will really consume so i will buy multimeter if i find cheap one and try measure after i get new psu.


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 Post subject:
PostPosted: Sat Oct 30, 2004 11:30 am 
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Your numbers still scare me, and I don't know how you've figured them out. Like the power drawn by memory. 22W? I'm sorry, but I don't f***ing think so.

And assuming 23.5W for DVD-RW and 24W for CD-RW is again just outrageous.

And you're still assuming 120W from your CPU.

You can EASILY get by with a normal 400W PSU, if not a 350W PSU.
EDIT: BTW, where in Europe do you live?

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 Post subject:
PostPosted: Sat Oct 30, 2004 2:44 pm 
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#1: Power draw for your Radeon is way too high. Even for an overclocked unit. Check out the power usage tables @ x-bit labs. You should lower your 5V line.

#2: Memory. Go by 2A @ 5V max per stick. You put at least double that.

#3: HDD. The values you put in there are for average run. That's OK. That's the value you should go by. But still note the startup value someplace for a final check. I don't know about the Raptor but even though Seagate site says the 7200.7 all use only the 12V line, it says different (5V & 12V both used) on the sticker on the hdd. You might want to take note of that too.

#4: I'd be very surprised if your mobo uses more than 20W max. Add a few (max 5W) for the onboard LAN and powering your USB mouse etc, you still top out at 25W. There's a reason everything on a mobo is passive cooled. If it was drawing 85W, you'd have mandatory active cooling in a couple of places.

#5: A PSU is usually relatively inefficient at low loads. So a lower powered PSU will produce less waste heat than a higherpowered one - again - usually. So don't rush to buy those 450+ monsters

#6: MikeC has again hit it on the head. A 400W will serve you fine. What you want to watch out for is the ratings on the 5V and 12V lines. Different PSUs have different balance. A 40A @ 5V PSU might be a bit too low on the 12V and fail to startup your hdds. A 30A @5V PSU that sags too much under high heat may not be able to power your Radeon.

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 Post subject:
PostPosted: Sat Oct 30, 2004 3:45 pm 
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z_unit wrote:
Cant, i am from Europe and it dont supports 220VAC.
Anyway i cant get psu just for try out here, but its curious to me how much power my pc will really consume so i will buy multimeter if i find cheap one and try measure after i get new psu.

Be very careful about how you use a multimeter to measure AC current -- it basically has to be in line with the AC input, which means dealing with 220VAC. Also, this will only tell you the CURRENT draw, which depends not only on actual power drawn but also the power factor of the PSU. Still, if you do this measurement on a PSU I have tested, we can still figure out what the real DC power draw of your system is.

Any bets on what it will be?

My guesstimate on DC power at absolutely full-tilt: Maybe 200W.

Regular readers of SPCR may recall the ARM Systems Powerhouse systemreview... It's componentry was almost exactly like what z_unit proposes here. It had a peak AC power draw of 236W. This translates (with the Zalman 400's efficiency of 75~76% at this power level) to ~180W DC power draw.

This is no reason for z_unit not to get a 600W PSU. Need and want are very different things. Lots of people around here buy 10 mi/gal cars with 300hp engines that can go 150mph even though the speed limit is 60mph & heavy traffic often makes it impossible to go much faster even if you want to break the law. If it feels good & lets you swagger and snicker a bit more convincingly, hey, as ego boosts go, it's pretty cheap & doesn't harm anyone. :lol: :lol: :lol:

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 Post subject:
PostPosted: Sun Oct 31, 2004 5:13 am 
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Yes my mistake, about memory i taken 4.4W (according to for this) for 4.4A, but 0.88A sounds wrong to so i put 2A there.
About radeon i added some more amps on +12V as well because i may upgrade to X800 some day.
sthayashi wrote:
And assuming 23.5W for DVD-RW and 24W for CD-RW is again just outrageous

>CD-RW
> DC +12V
> * Stand-by typical current: 450mA
> * Read typical current: 2A (52X read)
> * Write typical current: 2A (52X write)
> * Pause typical current: 1.2 A
> * Peak current: 2.5 A (OPC and spinup)


Anyway did not count them when i count 80% of total power as well as Floppy.


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 Post subject:
PostPosted: Sun Oct 31, 2004 7:46 am 
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You're building a system with TEN high power fans?? Shouldn't you be asking this on MonsterOverclocking.com or something? My AMD 2800+ system with a Radeon 9600 has two low speed 60mm fans (one case, one HSF) and does fine.

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 Post subject:
PostPosted: Mon Nov 01, 2004 3:39 am 
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Well CPU + VIDEO + PSU+ PSU + SYSTEM FRONT + SYSTEM REAR = 6
Plus i think to buy new case and i want get one with cooler under cpu build in case so it will be 7. Also i want 1 cooler on RAM and 1 on PCI so it will be 9.
And just in case my case will come with 2 rear coolers i add 1 more.
Cooler = better.


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 Post subject:
PostPosted: Mon Nov 01, 2004 5:10 am 
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Again, if your case fans pull down 0.7A, then you're not trying to be silent.

Looking at my 120mm L1A (More powerful than you're likely going to use), I see it's RATED for 0.24A. I've personally measured the current output on these fans and 0.24 is actually a bit high.

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 Post subject:
PostPosted: Mon Nov 01, 2004 7:11 am 
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z_unit wrote:
Cooler = better.

Not according to SPCR... cool enough with least possible noise level = best, since coolest possible will always be noisier.

Just out of curiosity: are you interested in silence at all or do you just want solid PSU advice? I ask since you already questioned SPCR's reason for being there in the first place and you are apparantly fine with a 55 dB noise rating...

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 Post subject:
PostPosted: Tue Nov 02, 2004 9:17 pm 
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Well, i am not sure now, i never think of building silent system before.
I could put silent (120mm) and fans of course, but my hdd (maxtor) do alot of noise anyway.
I need to think about this!


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 Post subject:
PostPosted: Tue Nov 02, 2004 10:42 pm 
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Well, join the club and build yourself a silent rig. Just don't expect it to happen overnight. A decent psu is a good starting point... I only have maxtors right now (4 of them) and even though they will get replaced at some point, they can be quieted down quite a bit with decoupling and some strategic damping.

From your PSU list I'd choose an Enermax... the quietest one, search will turn that one up (Noisetaker I believe). But I'd check out the Nexus 4090 as their fans are in a league of there own. A quality 400W with good efficiency is all you'll need IMO (and as others have said before).

I would rethink your fan needs though. Your RAM does not need a cooler of its own as long as the case has some airflow... which it will with a front and back fan. And why would you want a cooler on PCI? My rigs both have 120mm in and out which provide (more than) all the airflow I need.

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 Post subject:
PostPosted: Wed Nov 03, 2004 9:56 am 
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Hdd upgrade is my next step anyway just waiting when 16 MB hdd's will hit the market.
I think i build silent pc, yeah good idea i tired of noise already. I getting real noise from fans, it wont cost much to replace them. Plus with my new ThermalTake heatsink with 55 dB fan cpu temperature did not changed a bit from stock one. I think i already know which coolers i get UC-12FAB 94.92CFM with only 30.10dB :lol:.

Right now my case is something like midi tower with all this flat cables and bad airflow gets really hot even with 2x75 CFM fans.

To get back on topic i think i'll be getting Coolergiant VHB AX or Noisetaker AX when i get theyr dB rating somewhere.
Version of Noisetaker tested by SPCR, is not Active PFC :( and why its saying ATX 12V V1.3 compatible when enermax claim its ATX 12V V2.0 compatible.


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PostPosted: Wed Nov 03, 2004 10:06 am 
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If it seems too good to be true, it is usually not true.
Quote:
94.92CFM with only 30.10dB

Simply absolutely no way you can believe this. It would be true only if the sound meter was on another floor. :lol: :lol:

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 Post subject:
PostPosted: Wed Nov 03, 2004 10:52 am 
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MikeC wrote:
If it seems too good to be true, it is usually not true.
Quote:
94.92CFM with only 30.10dB

Simply absolutely no way you can believe this. It would be true only if the sound meter was on another floor. :lol: :lol:

Well why dont SPCR test this fan then?
Its just 14.99, but may be new word in silent cooling :o or big fubar who knows.


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PostPosted: Wed Nov 03, 2004 11:13 am 
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I have several variants of this fan. There is nothing unusual about it: It is a 2-ball bearing fan that obeys laws of physics. When spinning fast to produce high CFM, I'd guess the blades alone make enough turbulence noise (even without the motor!) to reach 30 dBA/1m. The 12V noise spec is out by 12~15 dBA/1m, probably more. I didn't check carefully, I have to admit, because once it goes past ~30 dBA/1m, it's pretty much irrelevant to SPCR.

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