Interesting System Wattage Table

[merlin]

The anandtech forums has an interesting post by Mr.Fox where a large number of systems were measured for peak and idle power usage. I think it's a great comparison to show what a modern system really uses for power. The main thing to note is that a good 300W psu can handle almost all non-sli/cf systems.

http://forums.anandtech.com/messageview ... erthread=y

[Aris]

this is old news around here. MikeC did a similar review over a year ago. He made a "then" high end gamming rig and a more casual web browser type system. I dont think load power consumption was much above 200w even on the gamming rig, and closer to 100w on the other system.

[jaganath]

this is old news around here.

nice to see realistic power numbers finally filtering into the mainstream.

[dhanson865]

3DMarks 06 with TAT and HD Tach and he still thinks he needs to add 33% to the max load on a quality power supply?

Didn't someone reveal the PCB on the Corsair HX620W is marked as a 700W or 750W part?

[EsaT]

Didn't someone reveal the PCB on the Corsair HX620W is marked as a 700W or 750W part?

Same PCB is used in 700W Seasonic M12 and 750W PC P&C Silencer.
(and 650W S12E+)

[merlin]

this is old news around here. MikeC did a similar review over a year ago. He made a "then" high end gamming rig and a more casual web browser type system. I dont think load power consumption was much above 200w even on the gamming rig, and closer to 100w on the other system.

I think you kinda missed the point here. This is a very large variety of gpu's measured on a very modern system which can be pointed to as FULL proof that systems do not need ridiculous 750w+ psu's most of the time. Mike's roundup is great, but there are far far far too many nonbelievers out there. We need to keep educating the public for the sake of good psu's and less waste. Promotion of low end high efficiency units is at least one good deed we can do.

[merlin]

3DMarks 06 with TAT and HD Tach and he still thinks he needs to add 33% to the max load on a quality power supply?

Didn't someone reveal the PCB on the Corsair HX620W is marked as a 700W or 750W part?

Ya I think 33% is a bit overkill, but that's just an extra column on the table, the key numbers are the actual load usage imho.

[Ryan Norton]

Durr, this really proves to me that I succumbed to "watts envy" when I bought the HX620 over the HX520... but the red IS nicer looking!

[jessekopelman]

Ya I think 33% is a bit overkill, but that's just an extra column on the table, the key numbers are the actual load usage imho.

Funny, because there is a whole crowd who think that you need 100% headroom. This seems to include the famed jonnyguru . . . You will notice some such folks on the anandtech thread from the OP. Personally, I think 33% headroom sounds about right, although 25% wouldn't be cutting it too close and 50% doesn't seem too extreme. Basically, the sweet spot would be somewhere between 25-50% overhead, depending on how conservative one likes to play it. Of course, proper thermal management is far more important. I bet a PSU could go a long time at 100% utilization if you could keep its immediate ambient temperature < 30C.

[dhanson865]

337W was the highest he got on any test without SLI or Crossfire and he was doing 20%+ overclocking.

S12-380 gives you 12.75% headroom
S12-430 gives you 27.5% headroom
VX450W gives you 33.5% headroom
M12-500 gives you 48.3% headroom
HX520W gives you 54.3% headroom
S12 E+ 550W gives you 63.2% headroom

All of that assuming he was measuring DC loads inside the case.

But lets be realistic here what percentage of the market buys quad core processors, overclocks them 20%+, and has 2 or more video cards?

I might get a tri core processor when they make one under 70W TDP that is also under $150 (I believe it'll have the Phenom X3 name) but I don't plan on heavy overclocking or multiple graphics cards (unless DX10 SLI/Crossfire boards get cheaper than I imagine). Until then I'm running a X2 processor and a single discrete video card, heck I'm even sporting discrete audio as well.

I really have a hard time imagining a system I would build that even with a 20% overclock would begin to ramp up the fan on a VX450W and that is in a single chamber case with no duct work or modding of any kind.

I could see if money was no object wanting a HX520W or an Energy+ 550W as a comfort purchase. But not because I'm worried about headroom.

If you ever hit 250 watts DC the M12-500 and S12 E+ tie as the quietest. If you ever hit 300 watts DC the HX520W is the quietest. At 200W you couldn't tell the difference between any of the 5 basic SPCR choices.

fwiw his lowest 100% load measurement was 179W which is still higher than the highest AC reading I've measured from any system I've ever built.

S12-380 gives you 112% headroom
S12-430 gives you 140% headroom
VX450W gives you 151% headroom
M12-500 gives you 179% headroom
HX520W gives you 190% headroom
S12 E+ 550W gives you 207% headroom

[NeilBlanchard]

Hello,

I'm wondering if the numbers used in this are the total AC consumption at the wall outlet? It is not stated clearly (that I could see), but he does mention "consumption" and that he does not take PSU efficiency into account.

Can someone who is a member of those forums post a specific question to clarify, whether it is "internal" DC consumption -- or "external" AC consumption, please?

[dhanson865]

Hello,

I'm wondering if the numbers used in this are the total AC consumption at the wall outlet? It is not stated clearly (that I could see), but he does mention "consumption" and that he does not take PSU efficiency into account.

Can someone who is a member of those forums post a specific question to clarify, whether it is "internal" DC consumption -- or "external" AC consumption, please?

smilingcrow (a name I'm assuming you've seen around SPCR) asked 09/22/2007 05:56 AM but I haven't seen a reply yet.

I’m not clear how the fluke was connected to the PC; are the measurements showing the AC power draw from the wall socket? I ask because in most tests looking at PC power consumption the values shown are AC power draw and some people don’t realise that power supplies are rated for DC output.
Therefore a System that consumes 300W AC with a power supply that is 80% efficient at that load is only outputting 240W DC. This misunderstanding is another reason why people over specify their power supply.

[andyb]

I massively overspecified my PSU requirements 500W of Phantom power, but at the time I was dead set on a passive PSU and a very quiet fan to cool it, and the Phantom 350W might not have cut my next upgrade (with headroom) and had just been discontinued.

In hindsight (the perfect science) I would have bought myself a 380W Seasonic S12 (again unreleased at the time).

My other machines are (1), 330W Seasonic S12, running a 3500+, a laptop HDD and an integrated graphics nVidia mobo. that never pulls more than 40-Watts (2), 380W Antec PSU that came with the original Sonata case, running 3200+ S754, nForce 3 Mobo, ancient PCI graphics card, 1x laptop HDD, 4x Samsung 500GB that I have never tested, but wont top 220-Watts.

Everyone has a safety limit, the difference is down to how big their safety limit is, availability, budget, and knowlege


Andy

[smilingcrow]

I'm wondering if the numbers used in this are the total AC consumption at the wall outlet? It is not stated clearly (that I could see), but he does mention "consumption" and that he does not take PSU efficiency into account.

I PM’d him and his response was:

‘The study was for AC Input, and was aimed at people to understand the peak demands of a PC.’

[smilingcrow]

Ya I think 33% is a bit overkill, but that's just an extra column on the table, the key numbers are the actual load usage imho.

He’s made the error of confusing AC input and DC output when calculating his headroom figures. So he’s saying that a PC that consumes 200W AC requires a power supply rated at 267W to give 33% headroom.
If the power supply on the 200W system was 85% efficient you would actually require a 226W power supply, including the headroom:

200 * 0.85 * 1.33 = 226W

This confusion over the difference between AC input and DC output contributes to people over specifying their power supplies.

[Techno Pride]

3DMarks 06 with TAT and HD Tach and he still thinks he needs to add 33% to the max load on a quality power supply?

Didn't someone reveal the PCB on the Corsair HX620W is marked as a 700W or 750W part?

The PCB may be labelled as such, but the components in the 620w PSU may not be able to handle a 700w load.

[ryboto]

well, at least they tried. The "super" admins on the sapphiretech forums will only recommend PCP&C and enermax power supplies. They consider FSP, Corsair, Seasonic, and low end silverstones to be "garbage". They only recommend units about 600W, and say that anything below that underpowers video cards.

[NeilBlanchard]

Hello,

So, they measured the AC consumption, and then added 33% to recommend the DC capacity of the PSU?! What this ends up being is ~48%-66% "safety" margin -- in addition to the PSU's actual safety margin.

Of course, in reality if the AC consumption is 200watt, then the DC actually used is ~140-170watts, depending on the efficiency, so adding the 33% to that yields ~186-226watt capacity on the power supply (instead of 266watts). You end up pretty close to the measured AC consumption...

[dhanson865]

I'd thought as much at first but gave him the benefit of doubt.

337W was the highest he got on any test without SLI or Crossfire and he was doing 20%+ overclocking. Just as importantly he measured AC load on a 80+ certified 850W power supply. 20% of 850 watts is 170 watts DC. Any reading he had below 212 watts AC is going to be even more inefficient. Assuming 80% efficiency at 300W for simplicity sake 337 watts AC = 270 watts DC. 33% on top of that suggests a 360 Watt power supply is sufficient for a quad core overclocked system.

again from 270 watts DC for a quad core overclocked system:

S12-380 gives you 40.7% headroom
S12-430 gives you 59.2% headroom
VX450W gives you 66.7% headroom
M12-500 gives you 85.2% headroom
HX520W gives you 92.6% headroom
S12 E+ 550W gives you 103.7% headroom

If you want to look at the rare top end quad core overlclocked dual video card (SLI) setup you have 504 watts AC * .80 for efficiency = 403 watts DC. Add 33% for margin and you get 536 watts for your top end.

from 403 watts DC on the highest consuming rig he could make:

S12-430 gives you 6.7% headroom
VX450W gives you 11.7% headroom
M12-500 gives you 24.1% headroom
HX520W gives you 29.0% headroom
S12 E+ 550W gives you 36.5% headroom

So unless you are that one in a million consumer that actually will fill every slot on your motherboard AND every drive bay AND overclock as much as possible, you should be able to get along just fine with a 450W power supply.

Of course the so called irresponsible journalism standard is still hanging over us considering that a mid range system will draw 142W DC at full load (quad core system measured at 229W AC).

There's a lot of these kinds of articles around. But I think they're irresponsible journalism because, as Nade points out, what's going to happen in a year.

Your PC might "typically" only pull 200 or 300W from the wall, but it's only going to tolerate being run at 50% or higher loads for so long.

[merlin]

I'm wondering if the numbers used in this are the total AC consumption at the wall outlet? It is not stated clearly (that I could see), but he does mention "consumption" and that he does not take PSU efficiency into account.

I PM’d him and his response was:

‘The study was for AC Input, and was aimed at people to understand the peak demands of a PC.’

I wasn't sure if he had some rather wasteful components in his computer, but seeing confirmation of ac input measurement...I can now safely say that ALL non-sli systems will work on a 300W psu, bare none! And all sli systems should work fine on a 500W psu! Of course this assumes no ridiculous overclocking and/or hoarde of components. My new mantra "Don't overbuy, Don't overbuy"

[EsaT]

Of course, in reality if the AC consumption is 200watt, then the DC actually used is ~140-170watts, depending on the efficiency

Here's some information about efficiency of that SilverStone PSU:
http://www.jonnyguru.com/review_details ... page_num=2
Crossload of first test will never happen in reality so tests 2 and 3 have relevant numbers.

well, at least they tried. The "super" admins on the sapphiretech forums will only recommend PCP&C and enermax power supplies...

And then even list some stone age design junks in their "reputable" PSU list.
Also they deleted my account and posts I made when I couple times showed real consumption numbers so that tells all that is needed to know about credibility of that forum and its superdorks. (calling them as admins/mods desecrates those words)