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PSU needs

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September 24, 2011 9:11:43 PM

How do determine how big a power supply you need when building you own system?

More about : psu

a b ) Power supply
September 24, 2011 9:19:37 PM

The PSU guide linked in my sig will help some.

There are a number of calculators out there... but here's how I usually do it.

I first discover how much power the graphics card(s) will pull from the PSU
http://forums.atomicmpc.com.au/index.php?showtopic=264

Then I add 200W for the rest of the system... a very generous amount that leaves a little margin.

That gives me a "max draw" from the PSU, so I know that is the minimum.

From there I look at what the normal load will be, whether gaming or whatever. This will be a number smaller than the max load. Then I try to fit a PSU that will be about double that. So that the PSU is operating at a max efficiency... but that is less important and may not be the case if you are trying to buy a PSU that will cover future upgrades.
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a c 248 ) Power supply
September 24, 2011 10:02:20 PM

The PSU calculators are overrated, they are simply a tool but without proper knowledge of how to use that tool they are wrong.


If you ever put in capacitor aging you now get vastly higher numbers than are true, it also doesnt have everything available and runs off of the rated TDP numbers, not experimental results.


Proximons method is good, the doubling for maximum efficiency can be a bit excessive but it does give you head room for additional upgrades. General rules of thumb, a good 500-600W unit will run any single GPU system, a 600-700W unit will run some dual GPU systems and most dual GPU cards, a 700-800W unit will run most dual card setups, a good 850W unit and above will run any dual card setup like dual 580s.
a b ) Power supply
September 24, 2011 10:14:59 PM

The information below will answer all of the OP's questions.

As far as PSUs are concerned, be informed. Before you buy any PSU read accurate, objective PSU reviews at reputable sites such as www.jonnyguru.com or www.hardwaresecrets.com on the EXACT model PSU that you are interested in as some brands have good and poor quality PSUs.

You can also get an accurate rating of how much PSU power is required for your current or future system at the PSU calculator link below. Once you know the total PSU watts required then you need to confirm that the 12v rail has enough amps. to support your Vid card(s) and the rest of the PC system.

There are several websites that show the Vid card power consumption in watts. Divide the watts by 12 to determine the amps. required on the 12v rail(s). Add 15 amps for the rest of the PC on the 12v rail and you now know the Minimum total 12v rail amps required under full load. It's best to have at least 5-10 amps. reserve on the 12v rail available under full load so the PSU is not loaded to 100%.

It's also worth noting that people often misunderstand the 80% power rating. This is a rating of the PSU's energy efficiency not it's output. 80% plus PSUs use less grid power to produce the same PC power. If it's 80% Bronze, Silver or Gold the cost savings on electricity is pretty small between Bronze, Silver and Gold unless you are paying very high rates for electricity so any 80% rated quality PSU is fine even if not Gold. For those who leave their PC on 24/7 a quality 80% PSU is a good investment.


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

http://www.guru3d.com/article/geforce-gtx-560-ti-sli-re...

http://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_5...

IT'S BETTER TO TEACH A PERSON HOW TO FISH THAN TO GIVE THEM A FISH FOR DINNER !
September 25, 2011 12:08:41 AM

Thanks for your reply just one question. What is "sig" ?
September 25, 2011 1:57:01 AM

Proximon said:
The PSU guide linked in my sig will help some.

There are a number of calculators out there... but here's how I usually do it.

I first discover how much power the graphics card(s) will pull from the PSU
http://forums.atomicmpc.com.au/index.php?showtopic=264

Then I add 200W for the rest of the system... a very generous amount that leaves a little margin.

That gives me a "max draw" from the PSU, so I know that is the minimum.

From there I look at what the normal load will be, whether gaming or whatever. This will be a number smaller than the max load. Then I try to fit a PSU that will be about double that. So that the PSU is operating at a max efficiency... but that is less important and may not be the case if you are trying to buy a PSU that will cover future upgrades.

a b ) Power supply
September 25, 2011 6:21:49 AM

Signature, the stuff at the bottom of my post, where it says "PSU Guide" :) 
September 25, 2011 10:10:14 AM

gigster said:
How do determine how big a power supply you need when building you own system?



I'm a big fan of Corsair products. My new build in progress contains their PSU, Case, SSD, RAM, and H100 liquid cooling.
I recommend using their PSU finder: Corsair PSU Finder
!