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i have been wondering lately, because i learned a little more, and because i have always done this, how is a power supply calculated if you just know the gpu, and how many gpus? i have always done it like this:

what the gpu draws from the wall-~10
+100 to 150 for the cpu(to my knowledge that is far more than it needs)
+100 for the rest of the system(again i have thought that this is overkill)

and i read these reviews that give 350 to the rest of the system instead of 250, just wondering how everyone else does it...

note: i am pretty sure this method works
 

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A modern system draws most of its power from the +12V, and of course the biggest consumer is the graphics card while the CPU is 2nd in line.

So I take the manufacturer's recommended power supply wattage, and I subtract about 50W since quality power supplies that we recommend are continuous, not peak-rated.

So if I see someone with an i7-920 and they want to upgrade from a GTX 460 to a GTX 580 with something like the Corsair's VX450, then I'll tell them to at least get something like the 550W TruePower New (at the very least). If they have a system like mine, then I just recommend a quality 550W unit without worrying about it.
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Quote:
Originally Posted by TwoCables;13148162
A modern system draws most of its power from the +12V, and of course the biggest consumer is the graphics card while the CPU is 2nd in line.

So I take the manufacturer's recommended power supply wattage, and I subtract about 50W since quality power supplies that we recommend are continuous, not peak-rated.

So if I see someone with an i7-920 and they want to upgrade from a GTX 460 to a GTX 580 with something like the Corsair's VX450, then I'll tell them to at least get something like the 550W TruePower New (at the very least). If they have a system like mine, then I just recommend a quality 550W unit without worrying about it.
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yep..... going by my method it would come up to 490w for 1 580, and i would say 550 or 500
 

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I like to use Newegg's online calcuator. Try your method against the one on Newegg, see how they compare. I usually round up to a effecient good quality PS from the reccomedation.
 

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Did they change the Newegg calculator? Or did they just pretend it wasn't vastly inflating results?
Urm... nope... the Egg still says I need nearly 800w, when I know for certain I could run this thing on a 650w unit with the right connectors...
If you're buying a top end unit, just ask around here, these calculators are designed around the PSU makers WHICH LIE and inflate their ratings massively.
Hopefully, when Nvidia and ATi shift their recommendations to only using 80+ PSUs then things may become more accurate.
 

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well.... i was expecting replies..... i guess i am disappointed..... i find this stuff interesting.... and fun..... oh well, i will stick to what i have been doing...
 

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Quote:


Originally Posted by Cvalley75
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I like to use Newegg's online calcuator. Try your method against the one on Newegg, see how they compare. I usually round up to a effecient good quality PS from the reccomedation.

That is actually one of the worst online PSU calculators on the internet. No OCN member should be using a PSU calculator, but if you must use one then use this one:

http://extreme.outervision.com/psucalculatorlite.jsp

However, I don't want any OCN members using even this one because they can get much better results by asking here in OCN's Power Supplies forum.

Quote:


Originally Posted by phantasmor
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well.... i was expecting replies..... i guess i am disappointed..... i find this stuff interesting.... and fun..... oh well, i will stick to what i have been doing...

It sometimes takes a while to get replies. Be patient; this thread is basically still a newborn.
 

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Discussion Starter #8
Quote:
Originally Posted by TwoCables;13154232
It sometimes takes a while to get replies. Be patient; this thread is basically still a newborn.
i guess.... i really find these things fascinating and i would really like to know how other people do it.... and i often wonder why people find these things mundane, i think anything to do with computer architecture is cool, especially the psu
 

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Quote:
Originally Posted by TwoCables;13154232
That is actually one of the worst online PSU calculators on the internet. No OCN member should be using a PSU calculator, but if you must use one then use this one:

http://extreme.outervision.com/psucalculatorlite.jsp

However, I don't want any OCN members using even this one because they can get much better results by asking here in OCN's Power Supplies forum.

It sometimes takes a while to get replies. Be patient; this thread is basically still a newborn.
lol their psu calc says i need around 800 watts for a [email protected] with 2 5970s and 3 hardrives and 10 fans i only got 1 5970 and 5870 but with clocks im running probly around 750-800watts.
 

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Quote:
Originally Posted by phantasmor;13157413
i guess.... i really find these things fascinating and i would really like to know how other people do it.... and i often wonder why people find these things mundane, i think anything to do with computer architecture is cool, especially the psu
I think one possible reason why people think PSUs are boring is perhaps because most people seem to think that a power supply is just a power supply. People are far more excited about things like CPUs and graphics cards because when they're upgraded, the difference is noticeable.

However, I think the PSU is my favorite part of the entire computer system! After all, the system is nothing without it.
smile.gif


Quote:
Originally Posted by Bal3Wolf;13157458
lol their psu calc says i need around 800 watts for a [email protected] with 2 5970s and 3 hardrives and 10 fans i only got 1 5970 and 5870 but with clocks im running probly around 750-800watts.
Interesting, because AMD recommends an 850W power supply to power a system with two 5970s in it!
 

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I still think the best method aside from asking the power gurus of OCN is to check actual power measurements.

The GPU and CPU are by far and away the biggest users of wattage, so just check review sites for their measured power usage stressing CPU and/or GPU and go with that. Even those will at times be inflated.

I got a kill-a-watt recently because I'm a sucker for knowledge, and hooked my system into it. Currently a 2600k @ 4.8GHZ (1.425V
frown.gif
) with an HD6950 2GB @ 6970speeds (not unlocked yet tho) and an H50. Running Prime95 + Furmark my system tops out at 365Watts (from the wall). So realistically I could be running one of the highest end systems around, heavily OC'd, on a 300Watt PSU lol.
 

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It would depend on the 300W unit - it would have to be quite a beast.
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Quote:


Originally Posted by Cvalley75
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I like that calculator, thanks for the link. I also have a Kill-a-watt, maybe I'll run the kill-a-watt on a few of my systems at full load & compare to the calculator linked.

If you do that, then take efficiency into account. So if the Kill A Watt is only reading what the PSU is pulling (what your system is pulling from the PSU), then multiply that number by values like .8 for 80%, or .85 for 85%.
 
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