# [SOLVED] How many watt power supply do I need?



## 2BlackRose2 (Apr 14, 2012)

Hi I'm doing a new build soon, Here are the specs:

Mobo: ASUS M5A78L-M LX
CPU: AMD FX-4100
RAM: Corsair XMS 4GB (1x4GB) DDR3 1333mhz
HDD: WD 500GB 7200rpm SATA II
GPU: HIS Radeon HD 6970

What is the minimum power supply I need? I know not to cheap out on a power supply but I am on a VERY limited budget?


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## greenbrucelee (Apr 24, 2007)

*Re: How many watt power supply do I need?*

the 6950 requires a 550w psu + 30% I would be running a 750w psu that is a good make.


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## 2BlackRose2 (Apr 14, 2012)

*Re: How many watt power supply do I need?*



greenbrucelee said:


> the 6950 requires a 550w psu + 30% I would be running a 750w psu that is a good make.


Would I be able to get by with a 600-650w?
I don't care about effeciency..as long as my budget gaming computer works good it and doesn't fry everything


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## Jooo (Jun 30, 2011)

*Re: How many watt power supply do I need?*



2BlackRose2 said:


> Would I be able to get by with a 600-650w?
> I don't care about effeciency..as long as my budget gaming computer works good it and doesn't fry everything


Yes. 

I suggest XFX Core Edition 450w for your system. Video card makers overestimate the power requirements for gpu's, to avoid any complaints against them so that all the crap quality 550w psus can run it. If you are getting high quality power supply you can remove 30% from the requirement: so you need minimum 400w high quality power supply.


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## greenbrucelee (Apr 24, 2007)

*Re: How many watt power supply do I need?*



Jooo said:


> Yes.
> 
> I suggest XFX Core Edition 450w for your system. Video card makers overestimate the power requirements for gpu's, to avoid any complaints against them so that all the crap quality 550w psus can run it. If you are getting high quality power supply you can remove 30% from the requirement: so you need minimum 400w high quality power supply.


You obviosuley have no idea.

I used to test power supplies for a living and test systems under load with graphics cards and other peripherals.

650w is correct and anyonye contemplating a 450w power supply for this system is either on drigs, doesn't have a clue about about computing and is plain stupid.


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## Jooo (Jun 30, 2011)

*Re: How many watt power supply do I need?*

Radeon HD 6970 Power Consumption and Thermals | bit-tech.net

Total system power consumption from wall, so again assuming 80% efficiency the power supply only needs to deliver 250W.


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## greenbrucelee (Apr 24, 2007)

*Re: How many watt power supply do I need?*

you dont seem to understrand. These results don't take into account power fluctuatons, component degredation and the wall outlet being perfect which is vary rarely the case in modern housing situations.

These testings are usually carried out in perfect conditions where as when I tested power supplies and systems for living we tested in perfect conditions and 'normal' conditions the result could be quite dramatic,

when figuring out a psu for your card and system you add 30% to what the main result is. 550w should be the minimum for any modern PCIe system then you factor in the gpu after that.


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## Laxer (Dec 28, 2010)

*Re: How many watt power supply do I need?*

To put in another opinion...

650W will run the system fine but IMO you would be better off with something closer to 750W.

Regardless of what wattage you go with I wouldn't put those components at risk on something less than 80+ bronze certified.

IMO, you would be lucky to find a quality PSU to fit your build for under $80.

If you don't have that to put in right now I would hold off until you can.


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## Jooo (Jun 30, 2011)

*Re: How many watt power supply do I need?*

Yeah right. Those reviews would not make any sense if they were made in "perfect conditions".

Here's another review, provenly done in perfectly normal conditions. AMD Radeon HD 6950 & 6970 (Cayman)

The first graph shows power consumption (full system excluding monitor)


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## Laxer (Dec 28, 2010)

*Re: How many watt power supply do I need?*

Interesting to read that review thanks for sharing.

Few things that might interest you and be informing to the OP.

No power supply is perfect, there is no such thing as 100% efficiency(perpetual motion). With that said, some power will be lost by the all components(mainly in the form of heat). An other concept to look at when dealing with power, things degrade over time, this is inevitable. I cannot remember the exact figure of wattage lost per year but it definitely does happen.

Our recommendations here are in no way a written law, we make suggestions based on our experience and knowledge on the subject. When we suggest something it is because we know that it will work.For what its worth... Based on your article a 5870 has a max draw of 254W. I have owned multiple of these cards and confirm that they draw far more then that.

My current set up runs 2 5870s, it would frequently crash when powered by a 750W PSU. (note: this is far above the suggested 508W by the article) Ended up upgrading to a 950W and would still even prefer a little more head room.


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## greenbrucelee (Apr 24, 2007)

*Re: How many watt power supply do I need?*



Laxer said:


> Interesting to read that review thanks for sharing.
> 
> Few things that might interest you and be informing to the OP.
> 
> ...


This is correct.

Depending on the quality of the power supply which seasonic made by power supplies (such as xfx pro, corsair AX,TH and TX models) and seasonics own can be upto 90% efficient however most are 80% for a good quality make.

Low quality makes such as kingwin, huntkey and rosewill are around 40-60% efficient.

A good quality psu that is specced for a system with 30% added to the wattage needed can loose around 5w a year. If a good quality make is specced for a system that is just enough to power it then you can tripple that figure.

A low quality make that is specced at total wattage needed plus 30% can loose 15w a year however a low quality make that is just enough to run the system can loose 50w a year but most of the time they will fail long before that.

Going for just enough to run your system is like just putting in enough petrol in you car to get you 20 miles and not taking into account that you may get stuck in traffic or have to find a longer route to your destination and then finding out you havent got enough petrol to get to a filling station to get back plus the fact it is not good for the engine.

Heads up Seasonic are working on a 95% efficient power supply but this is costing a lot of money at the moment because as Laxer pointed out 100% is not possible and 95% is very difficult.


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## 2BlackRose2 (Apr 14, 2012)

*Re: How many watt power supply do I need?*



greenbrucelee said:


> This is correct.
> A low quality make that is specced at total wattage needed plus 30% can loose 15w a year however a low quality make that is just enough to run the system can loose 50w a year but most of the time they will fail long before that. <Thanks for this helpful info>
> 
> Going for just enough to run your system is like just putting in enough petrol in you car to get you 20 miles and not taking into account that you may get stuck in traffic or have to find a longer route to your destination and then finding out you havent got enough petrol to get to a filling station to get back plus the fact it is not good for the engine.


So what power supply SHOULD I get? I'm REALLY stretched in budget
The only thing that confuses me about computers is power supplies
I know everything else. Just these annoying power supplies.
Anything under $80 might be okay.. I'm looking in the $60-70 range though

I HAVE changed my video card though.. To a $6870 because I can get a good deal on it... As far as I know the 6870 has slightly less TDP than the 6790, Correct me if I'm wrong, Though I know that slight difference makes almost no difference..


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## Johnny1982 (Oct 15, 2010)

*Re: How many watt power supply do I need?*



Jooo said:


> I suggest XFX Core Edition 450w for your system. Video card makers overestimate the power requirements for gpu's, to avoid any complaints against them so that all the crap quality 550w psus can run it. If you are getting high quality power supply you can remove 30% from the requirement: so you need minimum 400w high quality power supply.


DO NOT follow this advice, please. Greenbrucelee is correct for the HD6950 650w min or better still 750w to be safe.


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## Tyree (May 10, 2009)

*Re: How many watt power supply do I need?*



2BlackRose2 said:


> So what power supply SHOULD I get? I'm REALLY stretched in budget
> The only thing that confuses me about computers is power supplies
> I know everything else. Just these annoying power supplies.
> Anything under $80 might be okay.. I'm looking in the $60-70 range though
> ...


You need to be at 750W minimum for the 6970 as noted by the Techs.
If you drop the GPU to a 6870, you can use a 650W PSU but you are still looking at close to $100 for a good quality unit. SeaSonic XFX-Corsair (not the CX-GS-M Seroes)
The PSU is the last place you want to consider sacrificing quality to save a few dollars. If your funding isn't sufficient at this time, wait until they are or cut the costs somewhere else.
Added note: You will get better performance running a matched pair of RAM.


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