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PSU Wattage

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  • Power Supplies
  • Components
Last response: in Components
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September 4, 2011 1:13:14 AM

So I basically have everything picked out for my system except the power supply (I already bought my processor i5 2500k). Its going to have 8gb of ram, a 500gb harddrive, 560 ti 1gb. Everyone tells me that I need like 600 watts to run this system but I put all these things into a calculator that many people on here recomend and say is accurate, and I got like 450 watts. Thats with a overclocked cpu and all. So how much do I really need for my system?

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

More about : psu wattage

a c 77 ) Power supply
September 4, 2011 1:39:02 AM

You could possible run your system on a 450W power supply but I would recommend going with at least a 550W power supply. IMO... whenever you are building with a higher end graphics card, you should have a least 550W PSU or plan for at least 750W, if you think you'll Crossfire/SLI down the road.
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a c 157 ) Power supply
September 4, 2011 1:41:03 AM

A psu calculator is only as good as the input you give it.
Unfortunately you have no way to be accurate about some of the inputs. Maximum load, upgrades, capacitor aging etc.

A good old fashion rule of thumb will work best.

For a GTX560Ti you need 500w with 30a on the 12v rails plus two 6-pin PCI-E power leads according to EVGA.
That assumes a normal complement of hard drives, dvd's etc. Overclocking adds very little, it is the graphics card/s that primarily determine your needs.

If you think you might upgrade, here is a list for other graphics cards:

GTX570 needs 550w with 38a on the 12v rails plus two 6-pin PCI-E power leads.

GTX580 needs 600w with 42a on the 12v rails plus one 6-pin and one 8-pin PCI-E power lead.

GTX590 needs 700w with 50a on the 12v rails plus two 8-pin PCI-E power leads or 4 6-pin power leads.

It is not wrong to get a psu that is slightly stronger than your needs;

I suggest you get a quality psu. Cheap units may not deliver advertised power when you need it.
My short list of quality psu's includes Corsair, Antec, XFX, Seasonic, and PC P&C.
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a b ) Power supply
September 4, 2011 2:09:42 AM

The calculator works fine and calculates for max load of CPU and Vid card based on a 90% use of the PSUs available power. You can also allow for capacitor aging, etc. - if you read the information presented. You can plug in any future upgrades and run all different scenarios.

I have found the calculator to be quite accurate. It gives you the minimum amd the recommended PSU wattage. You can also adjust how much safety power you desire. Some folks like a 10-20% safety margin for future upgrades. If you input the proper info. into the calculator and it recommended a 450W PSU then that is all you need but you may find a 500W-650W PSU a better value if you intend to update down the road. If not, just buy a quality 450W PSU and be done with it.
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September 4, 2011 2:10:15 AM

Would 700w be enough for crossfire?
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a b ) Power supply
September 4, 2011 2:12:55 AM

krystianb10 said:
Would 700w be enough for crossfire?


Probably but enter your hardware into the calculator then check the 12V rail amps to be certain as that is the most import rail and the amps can vary consierably from PSU to PSU of the same wattage.

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

According to Nvidia the 560 TI 1 GB. uses 170W or ~14 amps per card max. So if you have a multi-rail PSU then you need at least 18 amps per rail to be safe or with a single rail PSU you'd need a minimum of ~55 amps total available on the 12V rail.

http://www.nvidia.com/object/product-geforce-gtx-560ti-...

Always read PSU reviews from repurable sources for the Exact PSU model you are interested in because Antec, Corsair and others sell some good PSUs and some not so good PSUs. Sources like Jonny Guru, Techpowerup and Hardware Secrets are reputable reviewers.
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