Anandtech PSU article

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

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Mats
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Anandtech PSU article

Post by Mats » Mon Sep 22, 2008 2:39 am

Here, haven't read it all yet.

lodestar
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Post by lodestar » Mon Sep 22, 2008 8:17 am

Well, according to that Anandtech article
Naturally, this is one of the benefits of choosing a power supply rated much higher than what you actually need: it will always stay virtually silent.
The power supply in question was a Coolermaster 900 watt unit, which here in the UK costs about £190. Ouch! But the basic point would seem to be for a quieter PC fit the largest power supply you can afford.

Tzupy
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Post by Tzupy » Mon Sep 22, 2008 8:41 am

Hmm, no. I suppose that by 'the largest' you mean 'the highest wattage', not the physically largest. :wink:
Anyway, buying a high wattage PSU may only guaratee high quality components and a fan that's ramping up slower.
A high wattage PSU may become great if you can swap the fan for a quality fan that has a maximum rpm of 60%-80% of the stock fan.
Of course, assuming you won't need more than 60% of it's rated maximum wattage for your system, which is usually the case.
If you try to use an even lower rpm fan, you might find out that it's not starting a the low voltage that the PSU is supplying at low load.
But some of the new and good PSUs use a 135-140 mm fan for which swapping is a problem, and the Enermax82+ uses a proprietary bi-voltage 120 mm fan.

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Post by Modo » Mon Sep 22, 2008 8:59 am

lodestar wrote:But the basic point would seem to be for a quieter PC fit the largest power supply you can afford.
Not really. If you check the graphs carefully, you will see that a 700W PSU is overkill for almost all systems, as it runs way below maximum efficiency most of the time, without really reducing the noise level. Basically, you want maximum system load to utilize the PSU at about 50%. If you consided that, then many, if not most, SPCR systems can do fine (sound-wise) with a 300W PSU. Even the gaming oriented rigs should be ok with "just" 500W (haven't seen many SLI/CF setups around here ;)).

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Post by FartingBob » Mon Sep 22, 2008 9:25 am

I look at it like this:
You want your PSU to be at its most efficient just above idle. This would be when your doing things like watching SD video, browsing the internet etc. Its these things you really want your system to be at its quietest and most efficient as its where most PC's probably spend the majority of their time.

silence is less of an issue when your stressing the GPU and CPU, as about the only thing that would do both is gaming, and then you have your volume up and you cant hear the PC anyway.
Of course there are exceptions, but this is true for most situations. As long as the PSU can handle the high peaks it doesnt have to do so silently.

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Post by jaganath » Mon Sep 22, 2008 10:20 am

the basic point would seem to be for a quieter PC fit the largest power supply you can afford.
this is completely wrong. for 99% of people, the best quiet versus cost proposition will be a very high quality, "low" wattage unit, such as Corsair VX450W or Seasonic S12-330/380. of couse, for gaming, where power load of 300W is possible, then something like Corsair HX520/620 is best. but 900W is just silly.

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Post by CA_Steve » Tue Sep 23, 2008 9:21 am

Ok, if you read through the article, it doesn't just focus on the benefits of a 900W supply. It does talk about the quiet benefit of having a supply over-rated for the load - and the author goes so far as to show typical load ranges for a couple of different PC configurations vs some typical PSU load vs dB charts. All in all, they did a decent job explaining some of the common PSU marketing fallacies and tried to point people in the right direction.

It might not have been a perfect article, but does it deserve to be bashed?

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Post by ryboto » Tue Sep 23, 2008 12:13 pm

I don't really trust anything Anandtech has to say after this article:
http://www.anandtech.com/casecoolingpsu ... i=3402&p=4

here's a quote: "The heatsinks are large and occupy almost all of the free space in the casing. Cooler Master advertises their use of small copper plates on the heatsinks as a means of increasing heat dissipation, since copper transfers heat faster than aluminum. Aluminum still dissipates the heat faster to the surrounding air, which is one reason the whole cooler isn't made of copper."

A review site that can't even get it's facts straight shouldn't be trusted.

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Post by continuum » Wed Sep 24, 2008 12:17 am

review site that can't even get it's facts straight shouldn't be trusted.
I agree there-- seeing the Aluminum vs. Copper myth alive and well on a site as major as Anandtech was extremely disappointing.

But that said, if you actually read the whole article, it's quite good-- especially because Anandtech has more than enough data points to personally assemble their own article on the topic of power supply sizing, efficiency, and noise-- and they can back it up with real numbers for SPCR-class enthusiasts who understand that all-- and for the layman they provide nice graphics with range boxes highlighted to emphasize exactly what's going on and make it very easy to visualize just how wasteful it is to buy the massively oversized PSUs everyone is selling today.

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Post by alecmg » Wed Sep 24, 2008 2:48 am

Are those power numbers on first page anything real? It looks to me they're too high, espessially idle ones.

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Post by riva2model64 » Tue Sep 30, 2008 4:01 pm

I noticed that power consumption results are not consistent from site to site.
eg, the link on the first post quotes the HD3850 as consuming 82w at load, where as another site I looked at says the HD3850 peaks at 63w, and a different site says the unit consumes 90w.

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Post by Meowbay » Thu Oct 02, 2008 1:53 am

That might be because some people overclock! I've once seen my system's total power-usage rise 33% using a couple of basic overlock settings in the BIOS. And I'm by no means specialized in overclocking, so I did not dare use excessive numbers.

By the way, why doesn't anyone mention the option to use 2 PSU's? I've been using a system with 2 fanless units with great success that way.

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Post by ryboto » Thu Oct 02, 2008 6:40 am

Meowbay wrote:That might be because some people overclock! I've once seen my system's total power-usage rise 33% using a couple of basic overlock settings in the BIOS. And I'm by no means specialized in overclocking, so I did not dare use excessive numbers.

By the way, why doesn't anyone mention the option to use 2 PSU's? I've been using a system with 2 fanless units with great success that way.
why does your system require two power supplies?

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Post by Meowbay » Mon Nov 03, 2008 6:58 am

ryboto wrote:why does your system require two power supplies?
Why does your system require power?

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Post by ryboto » Mon Nov 03, 2008 7:16 am

Meowbay wrote:
ryboto wrote:why does your system require two power supplies?
Why does your system require power?
I'm only asking because it seems extremely overkill unless you're going the multi-GPU + overclocking route.

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Post by Meowbay » Tue Nov 11, 2008 3:33 am

ryboto wrote:
Meowbay wrote:
ryboto wrote:why does your system require two power supplies?
Why does your system require power?
I'm only asking because it seems extremely overkill unless you're going the multi-GPU + overclocking route.
Actually, you're very wrong about that. Most PSU's are the most effective when under reasonably lower load. You seem to incorrectly assume that PSU's always pull from the power outlet what they're rated at for their maximum Wattage, but that's not the case!

Say you have 2 PSUs that can output 500 Watts each maximum, and your parts (for example 8 SATA drives in total, a real heavy CPU for rendering video and 3D) require a total of 460 Watts. Then it might be a lot more effective to use the two PSU's for that one system, so both PSU's give what they pull at both a real silent and a real cool state. Since it remains cool AND quiet you will not be needing extra fans, extra metal, extra power, and in addition both PSUs run at 80%+ I/O effectiveness.

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Post by ryboto » Tue Nov 11, 2008 8:30 am

Meowbay wrote:Actually, you're very wrong about that. Most PSU's are the most effective when under reasonably lower load. You seem to incorrectly assume that PSU's always pull from the power outlet what they're rated at for their maximum Wattage, but that's not the case!
When did I assume that? Where did I state that? Of course power supply's provide on demand power, and not their full rated power at any instant, why would you assume I was saying that??? Here's my take. A user gets an E8xxx series, or even a 65W AMD/Intel, gets two 100W video cards, and he only needs 265-280W of 12v. You can do that with a quality 400-460W power supply.

Also, the lower load quote is not totally accurate. Do you read SPCR reviews? Most newer models have a higher efficiency above 20% load up to 80-90% load.
Meowbay wrote: Say you have 2 PSUs that can output 500 Watts each maximum, and your parts (for example 8 SATA drives in total, a real heavy CPU for rendering video and 3D) require a total of 460 Watts. Then it might be a lot more effective to use the two PSU's for that one system, so both PSU's give what they pull at both a real silent and a real cool state. Since it remains cool AND quiet you will not be needing extra fans, extra metal, extra power, and in addition both PSUs run at 80%+ I/O effectiveness.
see, I imagine most users wont have 2 PSUs just sitting around, and that it will make less sense for them to buy two 500W, when they could get a single 550+W unit. It's rare that a typical user will completely load their system anyway. The added space requirement, and cost make this not the best alternative. I'm not saying it doesn't work for some people, it just isn't very practical.

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