What is an ideal power supply for this PC?

[VoraciousBear]

So I want to know what kind of power supply is enough to power this computer. This is what I am planning for my new gaming computer:

Crosshair III Formula 790x Mobo
AMD Phenom II x4 965 Deneb
8 GB Corsair XMS3 (1333)
Western Digital 640 GB HD 7200rpm
ATi 5970 graphics card
1 optical drive (DVD rewritable)


P.S. Glad I am building a new PC despite the fact that one of my friends says PC sucks and I should get a PS3. I turned him down. :p

[Wizrdwarts]

Re: What is an ideal power supply for this PC?

ATI's site says at least 650W.

[VoraciousBear]

Re: What is an ideal power supply for this PC?

ATI's site says at least 650W.

Interesting. I probably need a bit more due to the fact that my system is better than ATI's specified system. I was actually thinking of a 1000W PSU but maybe I don't need it.

[Wizrdwarts]

Re: What is an ideal power supply for this PC?

A good 650-750W PSU should be fine. 1000W is overkill unless you plan on upgrading a lot with more drives, Crossfire etc., and even then it's recommended 850W for dual 5970s.

[VoraciousBear]

Re: What is an ideal power supply for this PC?

A good 650-750W PSU should be fine. 1000W is overkill unless you plan on upgrading a lot with more drives, Crossfire etc., and even then it's recommended 850W for dual 5970s.

Should I go with a modular or non-modular PSU?

[Scinto]

Re: What is an ideal power supply for this PC?

Modular is so much easier to work with,

[KillerStickMan]

Re: What is an ideal power supply for this PC?

Should I go with a modular or non-modular PSU?

If you don't mind the extra cost, I would go with it.

[.Gunfire]

Re: What is an ideal power supply for this PC?

http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&Description=750w%20modular%20power%20supply&bop=And&ActiveSearchResult=True&Order=RATING

Choose one of these and you'll be fine :)

[Wizrdwarts]

Re: What is an ideal power supply for this PC?

Modular PSUs look better inside you case and it's a bit easier to work with your hardware since you have less wires in the way, but if you won't be seeing the inside of your case much (no case windows or anything like that), go with a non-modular PSU and save a bit of cash.

http://www.newegg.com/Product/Produc...e&Order=RATING

Choose one of these and you'll be fine :)

Nah, it's not just about the wattage, the 12V rail matters too. PSUs with the same wattage can have different amperage on the 12V rail, which graphics cards run off of. It's also safer to go with a major brand PSU than a cheap no-name brand.

[AlecJ32]

Re: What is an ideal power supply for this PC?

Just get a good, name brand (And name brand doesn't mean Rosewill or Raidmax, either) 500-600-700 watt unit, and you'll be good. I'd go with a Corsair or PC Power & Cooling, were it me.

Whatever you do, do not buy a 1000 watt unit unless your goal is to reduce your unit's efficiency. There is such a thing as an input efficiency curve, meaning that different loads have different levels of input efficiency. Efficieny tends to take a nose dive once you drop below 40% load.

If you want to do some power supply physics, let's make a hypothetical best/worse case situation and assume you have the choice between a high quality 600-(ish) watt power supply and a medium quality 1000-(ish) watt power supply, and your PC consumes 400 watts of power, which is a reasonable amount for a high end machine. With the 600-(ish) watt unit, 400 watts is right around the top of the efficiency curve, and you might get around 85% efficiency. However, with the 1000 watt unit, you're running at about 40% load, which might give you around 65% efficiency if we assume that the 1000-(ish) watt unit is not all that high quality.

400 watts / .85 percent efficiency = ~470 watts of power drawn at the wall
400 watts / .65 percent efficiency = ~615 watts of power drawn at the wall

And let's assume your PC uses 200 watts when not doing demanding use. Your efficiency with the 1000 watt unit might drop to 40%, and your efficiency for the 600 watt unit might drop to 78%.

200 watts / .78 percent efficiency = ~256 watts of power drawn at the wall
200 watts / .40 percent efficiency = ~500 watts of power drawn at the wall (seriously, that's bad, but we are talking worst case scenario)

That means between the two units, under load there's a difference of 145 watts drawn at the wall and idle there's a difference of 244 watts drawn at the wall.

Electricity is sold in kilowatt-Hours, not watts, so we have to convert watts to kilowatt hours. 0.145 kilowatts * 1 hour = 0.145 kilowatt-hours. 0.244 kilowatts * 1 hour = 0.244 kilowatt-hours.

Electricity goes for on average 12 cents per kilowatt-hour, so for every hour you game on your PC, it costs you 1.74 cents extra, and for every hour you leave your PC on but don't game, it costs you 2.928 cents extra. Now let's say you're a crazy bastard, and you game 6 hours a day and leave your PC on the rest of the time.

There's 8760 hours in a year, and 2190 are spent gaming while 6570 are spent 'idle'. 2190 * 1.74 = 3810.6 cents = ~3 dollars and 6570 * 2.928 = 19236.96 cents = ~192 dollars

So each year, that's about $195 extra which you'd be spending on electricity if you went with a mid-quality 1000 watt unit instead of a similarly-priced high quality 600-(ish) watt power supply.

Keep in mind though, this example makes a lot of assumptions, and is essentially a 'worse-case scenario'. This also is really only a problem with 1000 watt units, simply because your typical load is such a small percentage of the max output and because if it's the same price as a top of the line 650 watt unit, it's not going to be as high quality. You could get a say, 750 watt unit of good quality and not have to worry about this.