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How big of a power supply do i need?

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February 28, 2010 7:33:56 AM

I have used many PSU calculators and things like that, but i keep getting mixed results. So this is my first build, and im concerned with which power supply should i get. Im sure im getting a Corsair, but im stuck between a 750HX and a 850HX. I have one card for now, but i plan to crossfire in the future, so need help on which one i should get and how much does my current setup consume?

Setup:

CPU: Intel Core i7-920
Motherboard: Gigabyte x58a-ud3r
Ram: CORSAIR XMS3 6GB (3 x 2GB) DDR3 1600
Video Card: ATI HD 5850 (Planning to Crossfire in the future)
Hard Drives: Intel 40gb SSD and WD Black 1tb
Optical Drive: Lite-On DVD Burner
Fans: 5-6 fans with a Coolermaster v8 CPU cooler.

Sorry if this is a stupid question, but its my first build and i want to make sure i get whats best for my needs.

More about : big power supply

a c 248 ) Power supply
February 28, 2010 7:47:29 AM

Here are the official power requirements for the ATI Radeon HD 5850 and HD 5870 video cards.


ATI Radeon™ HD5850 System Requirements:

PCI Express® based PC is required with one X16 lane graphics slot available on the motherboard

500 Watt or greater power supply with two 75 watt, 6-pin, PCI Express® power connectors.

600 Watt or greater power supply with four 75 watt, 6-pin, PCI Express® power connectors for ATI CrossFireX™ technology in dual mode.


ATI Radeon™ HD5870 System Requirements:

PCI Express® based PC is required with one X16 lane graphics slot available on the motherboard.

500 Watt or greater power supply with two, 75 watt, 6-pin, PCI Express® power connectors.

600 Watt or greater power supply with four, 75 watt, 6-pin, PCI Express® connectors for ATI CrossFireX™ technology in dual mode.

The power supply recommendations are for an entire pc system.

The general rule of thumb is a high quality 500 to 550 watt power supply with sufficient current (amps) on the +12 volt rail(s) can easily power a system with any single video card made. A high quality 700 to 750 watt power supply with sufficient current (amps) on the +12 volt rail(s) can power a system with two video cards operating in dual mode. There are a few exceptions like the new ATI Radeon HD 5000 series cards which use less power due to their energy efficiency.

A high quality 500 to 550 watt psu will have a +12 volt rail rated at 40 amps. A high quality 700 to 750 watt psu will have a +12 volt rail rated at 60 amps.

In addition the power supply should be at least 80+ Bronze certified for energy efficiency. There are some models available which have achieved 80+ Silver and 80+ Gold Certifications.

Corsair and Seasonic are two of the brands that have a reputation for high quality power supplies that consistently earn high marks in technical reviews. They are reliable, stable, and come with a 5 year warranty. Some of the newer models come with a 7 year warranty. Lately we've been seeing a few other brands offering some high quality units.
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February 28, 2010 7:50:44 AM

The HX650 would be perfect, the HX750 and HX850 wouldn't hurt anything but your wallet. But if you want all that spare power, it's up to you :) 
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a c 141 ) Power supply
February 28, 2010 12:44:58 PM

There actually is a reason to buy an oversized PSU....peeps often spout 8- plus certified, ut the quoted efficiencies are never at the rated wattage.

Let's look at the soon to be released Antec SG-1200 for example

http://www.80plus.org/manu/psu/psu_reports/ANTEC_SG-120...

As you can see at rated wattage, the efficiency is 87% ....at 50% load it gets up to 90%. But then again, if only a small portion of the time spent on the PC is for gaming....in other words you work for a living, go to school, etc ....and use this PC to do it, for alarge part of that time you will be at the lower end of the power draw curve and efficiency goes down again....to 88% at 25% load.

Another thing to check is how stable the voltage is....the question is, can the PSU maintain clean and stable voltages at full load ? The answer is generally yes, in a top end PSU like the Antec SG / CP Series, Corsair HX series, Seasonic X series. Each tier drop in quality means that the PSU's power will get a bit noisier and voltage less stable as the PSU is stressed. Those looking for those extra 2 or 3 OC increments won't settle for anything but a 10.0 rating from jonnyguru.com. Most users will be happy with a 9.0

Both the Antec EA-650 and Corsair TX650 are appropriate for that build. To make the boost to an HX from Corsair or an SG or CP from Antec, you'd want a MoBo with a bit beefier power regulation subsystem on the MoBo (i.e. Asus P6X58D)
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February 28, 2010 9:38:38 PM

so with my set-up, with crossfire and maybe an LCD fan controller, i could pass with a 650W?
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a b ) Power supply
February 28, 2010 11:28:44 PM

You would be fine with 650w in a very good brand with high-efficiency. Good brands are Corsair, most Antec, Seasonic and most OCZ.

I would suggest (as others have already done) that you consider the corsair 650TX --currently $79.99 (after MIR) free shipping. 5 year warranty, high efficentcy, etc. You could actually crossfire 2 cards on the 550vx, but the 650 will give you better efficiency and some wiggle-room.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...
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