Help with PSU

[Pelasgos]

Greetings
I recently got msi 970 gaming, i5 4670k, gigabyte z170gaming mobo.
My psu is a chieftec 850 cft gdf.
My question is: is this psu good in terms of voltage stability and ripple supression?
Because I dont want to slowly kill my new parts.
Also, if it isnt, is the evga supernova g2 850 good to sustain OC and stable smooth gaming?
Please inform me.
Thank you.

 

[Norton]

Welcome to TPU!

That Chieftec psu looks like it was a 2009 unit- if it is that old I would definitely recommend replacing it- that EVGA G2 got a 9.9 out of 10 from JonnyGuru- I would really consider picking it up

See review:
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story6&reid=377

 

[n-ster]

No I wouldn't go with the G2 850W, as it is way overkill. The 650W G2 (or P2 if the price is similar) is probably your best bet, You could also consider something like the Corsair RM550x or RM650x (or i), but usually EVGA gives better value recently. Out of curiosity, what are the specs for the rest of your system? You can fill them out here: http://www.techpowerup.com/forums/account/specs

Your CPU uses practically nothing. TDP is technically 84 Watts, but that's always overrated and includes the IGP. My guess is that even with a decent overclock, we're talking 90-120W peak, probably 60-75W typical gaming usage?

Your GPU is something like 200W peak, you can assume that even the most demanding of games would probably not be able to replicate Furmark, so perhaps 160W during most gaming loads, maybe with a few peaks going in the higher 180s.

So with that said, a decent 360W would technically be enough really. Even with a second GTX 970, a 550W PSU would be enough, so with 650W you have tons of breathing room

 

[Pelasgos]

What do you mean by overkill? Its not a good PSU?
I updated my specs.

 

[n-ster]

I updated my post with some more info. Basically, your PSU would be under-utilized. Problems with having too big of a power supply aren't that big, just that it'll run less efficient mostly (ie: 85% efficient instead of 90%). In your case, since you are changing, other bad things about higher wattage PSUs are the physical size, often too long for more compact case which can become a factor in a few years if you ever upgrade etc, and obviously price.

Where do you live? Can you give us a price approximation for a Corsair RM550x, RM650x RM650i EVGA G2 650W and P2 650W ?

 

[Pelasgos]

I updated my post with some more info. Basically, your PSU would be under-utilized. Problems with having too big of a power supply aren't that big, just that it'll run less efficient mostly (ie: 85% efficient instead of 90%). In your case, since you are changing, other bad things about higher wattage PSUs are the physical size, often too long for more compact case which can become a factor in a few years if you ever upgrade etc, and obviously price.

Where do you live? Can you give us a price approximation for a Corsair RM550x, RM650x RM650i EVGA G2 650W and P2 650W ?

Thanks for answering.
Im in Greece and the price for both g2 650 and rm 650 is around 120 euros.
While the g2 850 is 160.
I remind you that I want a psu that has the most stable voltage and ripple suppression.
Which do you think of the above has the best?

 

[Jetster]

The less power the PSU puts out the more efferent it get not less. You can probably look this up.

I would just run the Chieftec 850 cft. Its not going to take anything out if it fails. I would stay away from the Corsair RM series I had two go out 650, 750. But a G2 650 would be nice. The G2 850 is on sale that why he mentioned it I think

 

[That Guy In The Shirt]

Thanks for answering.
Im in Greece and the price for both g2 650 and rm 650 is around 120 euros.
While the g2 850 is 160.
I remind you that I want a psu that has the most stable voltage and ripple suppression.
Which do you think of the above has the best?

The evga g2 650w psu is your best bet really. The g2 series is incredibly high quality, I know I'm happy with my 750w one. Your old cheftec psu probably isn't doing your build any favors, though I doubt it's really hurting anything either, but considering it's age and perhaps questionable build quality, it's going to crap out on you soon enough. EVGA's G2 series is incredibly well made, just look up reviews from sites like jonnyguru.com yourself and you'll see. The g2 650w would be perfect for powering your build, and that psu would last you quite a few years, well worth the money.

 

[m4gicfour]

The less power the PSU puts out the more efferent it get not less. You can probably look this up.

I'm only quoting you instead of everybody for simplicity sake, but it's not directed solely at you

Around 50% utilization is where most PSUs are most efficient. It falls off very slowly as you approach either extreme, both getting closer to maxing the capacity and getting closer to zero capacity. Each PSU responds a little differently, but generally speaking, unless you're using more than 90% capacity or less than 20% capacity, you'll be pretty close to the rated efficiency.


For example, the corsair I just replaced (upgraded from) was something like 90% efficient at 50% capacity, and went down to around 89% efficiency at low end, 87% at 100% of rated capacity.

 

[RejZoR]

You frankly don't need a 850W unit. I've done calculations and a 650W unit would be enough for my system in an overclocked state. I've gone with 750W just to be sure and since I already had that before.

The further you overshoot the need, the worse efficiency you'll have. Ideal is that your usual load falls within 50% usage. Which means you'll have best efficiency when running a bit more intensive stuff and when you're in idle, you'll still be in the good range of 20-25%. If you have too powerful unit, you'll never reach the 50% sweetspot during loads and when in idle, you'll be WAY below the low end sweet spot. Granted, the low end is really difficult these days since CPU's and graphic cards use so little power in idle, but still.

Best way if you're buying for existing system is to measure consumption with watt-o-meter for idle and very high load situations of your existing system.

Now take the watts measured and see where the measured consumption intersects with efficiency line of PSU that you want to buy. Bottom "limit" is usually 20%, the recommended load should be around 50%.

This way you get the best efficiency if you properly allign both consumptions to the highest efficiency you can get from a PSU you're looking at. Overshooting this by a lot by buying a way too powerful PSU means the idle will fall way below 20% sweetspot (which means you'll get poor efficiency when in idle) as well as the 50% which is where PSU's usually reach the highest efficiency.

Graph example:

See how the highest level is at around 50% mark and then starts to fall down? And how the 20% mark is very low and how it would go even lower if your % load of the whole unit is way below that? You can't get away with

Now lets do some calculations...

IDLE: 850W-80%=170W
LOAD: 850W-50%=425W

For 850W unit, this means your system should consume around 170W at idle and 425W when at load to achieve best efficiency. Considering not even my 22nm hexa core has such high consumption at idle, I'd say 850W is a massive overkill for your setup. And same applies for load...

IDLE: 750W-80%=150W
LOAD: 750W-50%=375W

IDLE: 650W-80%=130W
LOAD: 650W-50%=325W

See how sweet spots drop when you take weaker PSU...

When there were very little power saving features in hardware, it was easy. Measure consumption and pick a PSU that has idle and load the closest together at 50%. But today, gaps between idle and load are massive since hardware uses so little power in idle and has huge consumption at load and you have to use 20% and 50% points and decide based on that.

Alternate options are these PSU calculators:
http://www.bequiet.com/en/psucalculator
http://www.corsair.com/en/psu-finder
http://powersupplycalculator.net/
http://outervision.com/power-supply-calculator

Throw in as accurate setup of your system and you'll get a recommended PSU wattage. Be Quiet's calculator even estimates the loads so you can where different wattages fall into what load category. They of course list only their units, but basically if they are same efficiency level, they are comparable with PSU's from other vendors.