Please Suggest a suitable PSU


Dec 31, 2007

Please suggest a suitable PSU for following configuration.

MB: Gigabyte GA-B85-D3H
Processor: i5 - 4570
RAM: G.Skill RipjawsX 8 GB (2 X 4 GB)

Graphic card:
Asus 770 DC2OC 2 GB

DVD Writer : LG

I checked in online sites and each one is suggesting different wattages - 700, 535, 450.

How much watttage is needed and which PSU would be better.

I can spend $100~125.

It seems that the GPU needs 300W. The CPU needs 84 (let's say 100 to leave some headroom). They won't use this all the time, but you have to provision for it.

The motherbaord uses around 12-25W, the memory sticks usually around 7w, so also the fans up to 15w. Not sure how much the optical writer will.

I'd say you should look at minimum 500W. Personally I'd look at 650 -850W. I like high-efficiency (gold and platinum) power supplies and they are most efficient and coolest when they output around 50% of their rated capacity. But bear in mind that you will rarely demand the maximum power from your computer.

here is a list that I use to search through brands on offer on your favorite site.

Again, my personal preference lately is Seasonic and the high-end Corsairs. But it may change next time I build something. I'm not wedded to a brand and I will look around and evaluate any number of PSUs before I build.


In almost any single GPU setup these days all you need is a 500 or 550 quality supply. Unless you plan on doing something really unique or are doing CF/SLI setups there isn't much point in going much higher. You are probably pushing somewhere near 275-300 watts on the DC side of the supply when your machine is going at full capacity.

Something on the cheaper range would be:

Slightly More expensive, things like:



Just as an added note, if you take a look at Anand's test rig, their 770 machine was pulling a max of 314 watts from the wall ( ). Assuming their power supply is 92% efficient that would mean it was actually supplying 289 watts DC to the machine.

Even the 520 watt cheaper Seasonic is rated to supply 480 watts on it's 12v lines alone. Assuming every single watt of your machine was on the 12v line and you use 300 watts that puts you at a bit over 62% of the rated capacity. That's just about the sweet spot for efficiency and longevity and even leave you room if you change your gear out in the future to something that needs a little more power (since you want to stay below 80% of it's ratings as a general rule for longevity and reliability).



That's a fine supply, a little overpowered for what you need, but it's not like having too much capacity available is a problem.

Gold is technically better because it will be more efficient at converting the AC wall power to DC power for the components to use. More efficient means less heat generated for the same amount of power supplied. The difference isn't really all that huge once you get up in to the 85+% range though.

As an example, if your machine is consuming 300 watts and you have a bronze power supply it is 85% efficient. That means that it will use 352 watts from the wall to supply your machine with 300 watts DC, the remaining 52 watts will be lost as heat. If instead you had an 80Plus Gold supply it would instead use 333 watts from the wall (90% efficient) while supplying the same 300 watts to the machine. 33 Watts of heat would be generated, a difference of 19 watts.

Translated to cost, if you use your machine at full 300 watts for 3 hours per day and you pay 15 cents US per kW/h of electricity the 19 watts save would add up to 1710 watt hours per month, or 1.7kWh, or about 25.5 cents per month, about 3 bucks a year. If you expect your PSU to last 6 years you would save 18 bucks... so spending more than 18 bucks on the difference between the Bronze and Gold supplies doesn't make much sense.


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