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700w enough?

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September 17, 2012 3:21:57 PM

Hey guys.
I realise there is a guide on here about PSU's but it didn't really answer my question. At least I don't think it did.

I am about to upgrade my PC while utilising a couple of current pieces of hardware. The case, optical drive & the PSU.

My PSU says 700w on it. After some googling after checking it appears to be a CIT 700ub (Pictured below)



I have used online calculators and they suggest 610w of power.

My setup will be as follows:

i7 3770 3.4
Gigabyte GA-Z77-D3H
Corsair 16GB (2 x 8GB) 1333MHz DDR3
Toshiba 1TB 3.5" SATAIII HDD
OCZ 120GB Solid 3 SSD - 2.5" SATA-III
HD6970
1x CD/DVD drive
4x permenent USB pieces


1x 120mm case fan with LED
1x 80mm case fan with LED
1x stock CPU cooler.

I can't think of anything else that could draw power. I am just wondering if my PSU would be enough?

Any questions I will do my best to answer.

Thanks

More about : 700w

a b ) Power supply
September 17, 2012 4:25:23 PM

It sounds really risky to me.

Regardless what it says on the box, a PSU will usually give you about 10w for every $1 USD in the base price. This thing goes for maybe 40 or 45 USD, so I wouldn't trust it for more than 400 - 450 real watts.

The safest bet would be to get a 600w from a good brand that is priced like an actual 600w (more like $60ish). The Corsair CX600w is an example, Corsair TX 650w and XFX Pro 650w Core are other high quality PSUs in the range.

None of that means that you can't kinda sorta try to get by with the one you showed up there. You most certainly can and it may even work the first time you turn it on. That being said, cheapy PSUs are well known to blow up and cause irrepairable damage to motherboards, video cards, hard drives, and so on.

Getting a real PSU that is high quality is like having an insurance policy on all those things.

PSUs in general are all kinda like ticking time bombs regardless of what they are, you just want the countdown timer to be really really long. Cheapy PSUs don't give you that.
a b ) Power supply
September 17, 2012 4:32:25 PM

700 watts without a 80% efficiency is about 560 watts peak power at best so yes you can pull it off for a while but don't risk it, sell that POS for 20 bucks and use the rest against the price of one of the excellent PSU's suggested above.

If you have no cash at all yes use it but no stress testing or overclocking at all.
Related resources
a b ) Power supply
September 17, 2012 4:32:56 PM

Not nearly big enough. The last thing you want to do is scrimp on a PSU. Buy the highest wattage QUALITY PSU you can afford. Using a small PSU is like running your car in first gear. It will fail beforwe its time.
a b ) Power supply
September 17, 2012 4:40:15 PM

I have issues with both of the last two posts. Spentshells, a PSU's efficiency does not cut into its peak power. It works the other way: a PSU running at 80% efficiency will draw 625W from the wall when the computer needs 500W. 500W, the actual useful power, is 80% of the load from the wall. If your claim were true, every PSU would actually deliver far less than its rated load, and that's not the case.
Ram, a high-wattage PSU is often just wasteful when the rest of its build isn't crazily high-end. The efficiency of a PSU depends on its load, and the relationship generally looks something like this:

A 6970 build will only actually draw something like 350W, according to this review: http://www.bit-tech.net/hardware/graphics/2010/12/15/at...
Therefore, a 1000W PSU (for instance) would actually be quite a bit less efficient than, say, a 600W one under 300W of load. The above chart is for a 900W PSU, and it's got abysmal efficiency until around 300W. A 1000W box would be worse.
It's generally best to get a PSU with a decent amount of overhead, as Raiddinn says, but that doesn't mean you should get the highest-wattage PSU possible.
a b ) Power supply
September 17, 2012 4:43:03 PM

Spentshells - The point you are trying to make is completely wrong. Efficiency is on the other side of the calculation.

Take my PSU for example, XFX Pro 650w Core. Say it is 80% efficient and I load it to the max and the max is accurate as labeled. I can still access that whole 650w, it will just mean that I have to draw 650w / 0.8 = 812.5w from the wall.

Some PSUs are overlabeled, but that has zero to do with efficiency.

If that CIT 700w is an overlabeled 400w as I suspect, it could still give the whole 400w, it would just pull 500w from the wall to do so.

Whatever is on the label you are supposed to be able to access the entire amount for your components. The problem is just that a lot of makers lie on the label, the problem has nothing to do with efficiency at all.

- Edit - kajabla owns me in posting speed.
September 17, 2012 4:45:07 PM

Agree with Raiddinn ^

I would not ever have such a cheap PSU in a nice setup like that.

Notice how it only has 21 amps on the +12v rail? A 550 watt PSU from Corsair's middle of the road line has 45 amps on the +12v rail. Also, your PSU has higher amps on the +5v rail which used to be needed many years ago but is no longer.

Just so you can see the sticker im not recommending this PSU:

http://www.jonnyguru.com/modules.php?name=NDReviews&op=...
September 17, 2012 4:50:10 PM

Basically my choice is either a PSU or an upgrade to my GPU. Obviously I was aiming for a 6970. I currently have a 450GTS. It looks like I am going to have to go for a PSU. Not as fun though. Safety first I guess.

I was going to buy the 6970 for £130 from a friend. could anyone suggest a PSU around the £100 mark, or less if there is one that would suit my needs?

Thank's a lot for all of the advice guys.
September 17, 2012 5:13:30 PM

Good call on the PSU.

If you want to do your own research take a look at http://www.jonnyguru.com and http://www.hardocp.com/ These two do the best testing of PSU's bar none.

If your not going to Crossfire the GPU's then a quality 500-600 watt PSU will be fine for any single GPU build. Something like the Seasonic 560W http://www.amazon.com/Seasonic-560W-Plus-Power-Supply/d.... That PSU gives you 46 amps on the 12v rail which means it can actually provide 550 watts on the +12v rail alone(Just saying unlike your 700 watt this one will put out much more than its rated 560w)

You have a pretty high quality setup so I wouldn't go much lower end in the PSU department.

Edit: Changed to Amazon link since newegg link was not working.
a b ) Power supply
September 17, 2012 5:45:23 PM

That is indeed an example of a high quality PSU. The Corsair TX models, all of them, get the highest quality marks on most serious reviews that involve using testing hardware.

It is kinda overkill, though. There is no way you would even be able to come close to maxing that thing. A Corsair TX 650w or XFX Pro 650w is cheaper and still well in the safe zone.
September 17, 2012 5:48:40 PM

A TX650 from the vendor I use is actually £20 more expensive? That there is the cheapest Corsair PSU they suppy.
a b ) Power supply
September 17, 2012 5:54:40 PM

Weird, I guess if the 750 is cheaper than the 650 for whatever reason then get the 750. It isn't usually that way, but there are always deals that can disrupt the natural order of things.
a b ) Power supply
September 17, 2012 6:32:28 PM

kajabla said:
I have issues with both of the last two posts. Spentshells, a PSU's efficiency does not cut into its peak power. It works the other way: a PSU running at 80% efficiency will draw 625W from the wall when the computer needs 500W. 500W, the actual useful power, is 80% of the load from the wall. If your claim were true, every PSU would actually deliver far less than its rated load, and that's not the case.
Ram, a high-wattage PSU is often just wasteful when the rest of its build isn't crazily high-end. The efficiency of a PSU depends on its load, and the relationship generally looks something like this:
http://images.anandtech.com/reviews/psu/2008/cooler-master-ucp-900w/eff-comparison.png
A 6970 build will only actually draw something like 350W, according to this review: http://www.bit-tech.net/hardware/graphics/2010/12/15/at...
Therefore, a 1000W PSU (for instance) would actually be quite a bit less efficient than, say, a 600W one under 300W of load. The above chart is for a 900W PSU, and it's got abysmal efficiency until around 300W. A 1000W box would be worse.
It's generally best to get a PSU with a decent amount of overhead, as Raiddinn says, but that doesn't mean you should get the highest-wattage PSU possible.



If you have a problem with my statement buy the same PSU put your computer on it then load it up....
giver
a b ) Power supply
September 17, 2012 6:36:09 PM

Raiddinn said:
Spentshells - The point you are trying to make is completely wrong. Efficiency is on the other side of the calculation.

Take my PSU for example, XFX Pro 650w Core. Say it is 80% efficient and I load it to the max and the max is accurate as labeled. I can still access that whole 650w, it will just mean that I have to draw 650w / 0.8 = 812.5w from the wall.

Some PSUs are overlabeled, but that has zero to do with efficiency.

If that CIT 700w is an overlabeled 400w as I suspect, it could still give the whole 400w, it would just pull 500w from the wall to do so.

Whatever is on the label you are supposed to be able to access the entire amount for your components. The problem is just that a lot of makers lie on the label, the problem has nothing to do with efficiency at all.

- Edit - kajabla owns me in posting speed.


so 80% efficiency at putting out 700 watts (which it obviously can not do) is wrong or is marking a 500 watt PSU as 700 watts wrong ?
a b ) Power supply
September 17, 2012 6:38:00 PM

Raiddinn said:
Spentshells - The point you are trying to make is completely wrong. Efficiency is on the other side of the calculation.

Take my PSU for example, XFX Pro 650w Core. Say it is 80% efficient and I load it to the max and the max is accurate as labeled. I can still access that whole 650w, it will just mean that I have to draw 650w / 0.8 = 812.5w from the wall.

Some PSUs are overlabeled, but that has zero to do with efficiency.

If that CIT 700w is an overlabeled 400w as I suspect, it could still give the whole 400w, it would just pull 500w from the wall to do so.

Whatever is on the label you are supposed to be able to access the entire amount for your components. The problem is just that a lot of makers lie on the label, the problem has nothing to do with efficiency at all.

- Edit - kajabla owns me in posting speed.


This is all theoretical since already we know in reality this thing can not put out 700 watts

so despite the math I threw out like puke is wrong in all honnesty Im right
a b ) Power supply
September 17, 2012 6:46:04 PM

The PSU the OP is looking at sucks, but its not for the reason you said. That is the point.

If someone has a PSU that is a real 700w, then it will really do the whole 700w. It will just take 700w / 0.8 = 860w(ish?) from the wall to do it at 80% efficiency.

I just want to point out to the OP that:
1) They don't need to plan on their PSU not being able to give out its stated wattage if its a good one
2) Tell you what the situation really is in regards to efficiency so you know for the future
3) Tell anyone else that reads this thread how this all really works
September 17, 2012 6:47:58 PM

Please guys. Keep cool. I'm just looking for some advice here. I am going for the Corsair CX750 that I saw. I thank you for the advice you gave me.
September 17, 2012 6:52:35 PM

I don't think you need a new psu for your build.

http://www.bit-tech.net/hardware/graphics/2010/12/15/at...

That bit-tech.net article showed a 130w i7 965 and hd6970 pulling 306w FROM THE WALL while running 3dMARK
2K6 canyon flight at 1280x1024 no aa and 16x af. You have a i7 3770(non k) 77w cpu and while the max tdp on
a hd6970 is 250w, it's more like 190w when gaming. I am guessing you are weighting this build more for work
than play, since you are getting an i7 and 16GB of ram versus an i5, 8GB of ram and an hd7850 that costs
about the same as hd6950(130) but runs as fast as hd6970 in some titles(faster when OCed) and uses far less
power. That 700w psu of yours has TWO +12v rails at 21A(252w) EACH. That is a total of 504w of +12v power
available to parts. Almost all parts use +12v power nowadays, either directly or indirectly, and the cpu and gpu
are by far the biggest culprits. You probably won't max out the 3770 while working, and it plus the hd6970 won't
draw anywhere near their max tdp while gaming.

I would guess that the rails are divided up so that one of the +12v rails goes exclusively to the mobo(power
circuits, chipset, cpu, ram, PEG slot, add in cards, usb devices, cpu fan and maybe case fans) while the other
+12v rail is for additional pcie connectors, drives and case fans.

I might suggest upping your gpu budget to 160 (which includes delivery/carriage/shipping and VAT) to get a
HD7850. Here are a few links to ones on sale at scan and overclockers in the UK:

http://www.scan.co.uk/products/2gb-xfx-radeon-hd-7850-c...

http://www.overclockers.co.uk/showproduct.php?prodid=GX...

Here's a launch review of HD7850 at hardocp (read results on the game pages and ignore the conclusion page):

http://www.hardocp.com/article/2012/03/04/amd_radeon_hd...

Here's a launch review of HD7850 at techreport(I'm linking the last page, but the whole article is good):

http://techreport.com/review/22573/amd-radeon-hd-7870-g...

Here's a review of gtx660 at hardocp(has HD7850 mildly OCed with the latest drivers and gtx570 aka HD6970):

http://hardocp.com/article/2012/09/13/asus_geforce_gtx_...

Here's a gtx660 review at techreport including a reference clocked hd7850(test method page wrong)w/12.7 beta:

http://techreport.com/review/23527/nvidia-geforce-gtx-6...

The HD7850 is much cheaper now, faster now with newer drivers, and is highly overclockable.
September 17, 2012 6:57:12 PM

Well that throws the cat among the pigeons. Just as I think I am sorted, someone does that....lol
September 17, 2012 7:03:08 PM

the reason the cx750 is cheaper than the tx650 is because the cx builder line are corsair's cheapest power supplies.
TX,HX and AX are the more enthusiast supplies(better fans, components, higher +12v rails), and the GS gamer
series is in the middle. I hope I'm not too late and you can save money by not buying a psu you don't need and
better spending a few extra bucks on a better gpu.(lower wattage, too.)
September 17, 2012 7:03:34 PM

Thank goodness I caught you in time!
September 17, 2012 7:07:57 PM

Well, my amended list is


i7 3770 3.4GHz
Gigabyte GA-Z77-D3H
Corsair 16GB (2 x 8GB) 1333MHz DDR3
Toshiba 1TB 3.5" SATAIII HDD
Corsair TX 750W V2 PSU

I have taken away the SSD (I only put it there for vanity. Boot times are of no conciquence to me really. This is a work machine) and added the Corsair PSU. So I will only be spending £30 more to get the PSU. It seems the general opinion that it is a good idea to get one anyway.

This leaves around £150 for my GPU. This number is SLIGHTLY changable.
September 17, 2012 7:14:49 PM

People didn't look at the label on your current psu close enough. a tx750 is total overkill for your build.

If you want a gpu for gaming(bf3 online, anyone?), an ssd can help you switch maps faster than opponents.


a c 83 ) Power supply
September 17, 2012 7:15:24 PM

kajabla is right about 80+. Its all about power efficiency and less power waste(HEAT).

A 60% efficient power supply will still deliver its rated wattage. It will just push more heat as well. This said power supplies are rated in DC voltage not AC voltage.

Since the power supply is question lacks the combined 12 volt current, i have to resort to taking everything off too see the minimum amount that can remain.

700 watts total
95.7 watts on 3.3(3.3 x 29)
160 watts on 4 (5 x 32)
3.6 watts on -12(0.3 x 12)
12.5 on 5v standby(2.5 x 5)
271.8 watts used
428.2 left or a bit over 35 amps. is the MIN that this power supply should be able to deliver.

The problem here is that this is very hit and miss since the designer of this power supply may have shared the 3.3 + 5 volt rails leaving more 12 volt current left, but without proper numbers this is my best guess.

Modern power supplies have one huge 12 volt rail and get the others from it. This is how you can now get a 700 watt power supply with 680watts @ 12 volts. This all assumes that the 3.3 and 5 volt usage is kept to a minimum. As the 3.3 and 5 volt use increases it does cannibalize the large 12 volt rail.

From a pure power point, i would guess it would work, BUT from a quality point of view I have some fear for your system.

That corsair unit you posted(CX 750) was FAR better and offers 744 watts(3.3/5 volt rail use allowing) on its 12 volt rail(That runs your system with tons of spare power for anything you toss in down the line).
a b ) Power supply
September 17, 2012 7:16:16 PM

My bad, I thought the original link was a TX 750, not a CX 750.

Anyway, both CX and TX do pretty well. A CX 600w is more than good enough for the whole PC, regardless of which video card gets chosen.

There isn't really a need to go for a TX 750w, but there is still, IMO, a definite need not to go with the CIT 700w.
a b ) Power supply
September 17, 2012 7:18:36 PM

^ the CX 750 would be OK, CX is really kind of midlevel quailty, personnaly I'd go for the TX650, but that is me.

Reading the Post just some general comments.
1) Rated verse Real power output is NOT related to eff. (although it tends to work that way). The reason Low end PSUs do NOT provide rated output is due to deregulation based on temps. Low end PSUs rate the PSU based on a 20-22 C temp as componet temps go up output capability goes down so when it reachs 40C the output is limited to 50-60% of rated value. GOOD PSUs will provide rated output upto normal operating temps AT RATED load. PS a Series regulated PSU will beat the pants off of a 80% switching PSU for stability and regulation with less noise, BUT its eff. is terrible (50->60%), plus much larger and heavier.
2) If Power @ load is say 400 Watts a 650 Watt PSU (80%) and a 850W rated at 80% will draw almost the same power from the outlet (slightly more for the 1KV but not enough to pay for my dily coffee LOL.
It is the LOW end (idle power) that favors the 650. At Idle the power is down around 150 Watts. For the 650 Watt PSU is around 23% utlization, but for the 850 it is only 17% This might buy me a cup of Coffee per week @ starbucks.
September 17, 2012 7:33:33 PM

3.3v and 5v are hardly used anymore. 5vsb(stand by) is only used when the system is off. -12v is practically
inconsequential. The bit-tech article that has been linked twice now has a 130w i7 965, a power hungry x58 mobo,
6GB ram,128GB ssd & hd6970 pulling 306w from the wall on a 80+ corsair hx1000 psu. That means the actual power
delivered may have been closer to 260w. Rich will have a i7 3770(non k) at 77w, a less power hungry z77 mobo,
1TB HDD, 16GB ram, optical drive, maybe a 128GB ssd, and either a hd6970(250w in 3d mark?, 190w during typical
gaming) or a HD7850(140w max, likely much less while gaming). You don't think Rich's current psu can pull at least
50%(or substantially less even) of its 504w +12v capacity?
September 17, 2012 7:37:57 PM

I meant 250w delivered by the hx1000 in that load test(3d mark 2006).
a c 83 ) Power supply
September 17, 2012 7:45:25 PM

jtenorj said:
3.3v and 5v are hardly used anymore. 5vsb(stand by) is only used when the system is off. -12v is practically
inconsequential. The bit-tech article that has been linked twice now has a 130w i7 965, a power hungry x58 mobo,
6GB ram,128GB ssd & hd6970 pulling 306w from the wall on a 80+ corsair hx1000 psu. That means the actual power
delivered may have been closer to 260w. Rich will have a i7 3770(non k) at 77w, a less power hungry z77 mobo,
1TB HDD, 16GB ram, optical drive, maybe a 128GB ssd, and either a hd6970(250w in 3d mark?, 190w during typical
gaming) or a HD7850(140w max, likely much less while gaming). You don't think Rich's current psu can pull at least
50%(or substantially less even) of its 504w +12v capacity?

I am more worried about the quality of the power supply then its actual rating. A good 500 watt would run the system with ease.

I have yet to pull over 300 watts @ the wall on my personal system. My older ones did, but everything just gets more and more power efficient.

My i7 920(3.5, but with power savings idles are the same) system took more power at idle(150 watts or so) VS the 85-90 of my 2600K system. My media center can pull off 40 watts with a 5770 and i5 750 at a dead idle and has trouble passing 180(it has not) at the wall when gaming with Prime95 running.

I have more fear of the quality of the power supply(but have no experience with that unit to say yes or no for sure) then anything else. Not the actual wattage rating.

Many also complain about bestek and other HP power supplies, but I have put some of those under some good stress without ever having an issue.
September 17, 2012 7:56:26 PM

The parts in a pc never pull their max tdp all at once either. During a game, maybe the optical drive gets polled
at launch for anti piracy reasons, and the hdd gets accessed between rounds loading levels(BF3). The cpu and
gpu don't get fully utilized until in round. During work with the i7 3770, the gpu will likely be in desktop mode,
running at much lower core and memory clocks and drawing far less power than at load. An ssd would sip power
moving from one map to the next in BF3, btw. Just get a decent capacity hdd for pics, music and movies(it can
be lower rpm, lower power, lower heat for those simple sequential files) and put os, games, and other apps
(browsers, office suites, other productivity apps) on the ssd for snappier performance. Even the best consumer
spinners(1TB 2.5in 10k rpm raptors) have only 333 random 4k iops . SSDs generally have anywhere from tens
of thousands to over 100k iops. They will not only load windows faster, but everything else, too.
a b ) Power supply
September 17, 2012 8:05:58 PM

Raiddinn said:
The PSU the OP is looking at sucks, but its not for the reason you said. That is the point.

If someone has a PSU that is a real 700w, then it will really do the whole 700w. It will just take 700w / 0.8 = 860w(ish?) from the wall to do it at 80% efficiency.

I just want to point out to the OP that:
1) They don't need to plan on their PSU not being able to give out its stated wattage if its a good one
2) Tell you what the situation really is in regards to efficiency so you know for the future
3) Tell anyone else that reads this thread how this all really works



SO it sucks and can not do exactly what I said it can not do for different reasons I can accept that.

On a side not if a psu can output more than it is rated trust me it is always mentioned on the PSU as peak wattage this used to be the norm but somehow marketing wizards managed to wiggle around that and use numbers not at all possible by the PSU. This was 2002 and SPARKLE was up the.re with PCNP, SPARKLE unfortunately went the way of making a prototype that could produce the claimed wattage then put out a POS that could not onto the unsuspecting market
It's hard to apply the real logic you are using on a device that is already using false claim.

In retrospect I am wrong in the way I applied the math but at the same time there was never a real number anyway. Thanks for the the pointers
September 17, 2012 8:07:43 PM

FYI, order placed. these numbers are BEFORE tax.


Item: Zotac GTX 660 2GB GDDR5 Dual DVI HDMI DisplayPort PCI-E Graphics Card
Qty: 1 Cost: £149.99

Item: Intel Core i7 3770 3.4GHz Socket 1155 8MB Cache Retail Boxed Processor
Qty: 1 Cost: £189.81

Item: Gigabyte GA-Z77-D3H Socket 1155 VGA DVI HDMI 8 Channel Audio ATX Motherboard
Qty: 1 Cost: £65.61

Item: Toshiba 1TB 3.5
Qty: 1 Cost: £45.83

Item: Kingston 8GB DDR3 1333MHz Memory Module Non-ECC CL9
Qty: 2 Cost: £23.46

Item: Corsair TX 750W V2 PSU - 80plus Bronze Certified
Qty: 1 Cost: £69.40
a c 83 ) Power supply
September 17, 2012 8:24:55 PM

Well, you will not find a single video card that will overload that power supply :) 
a b ) Power supply
September 17, 2012 8:27:40 PM

Grats, hope everything arrives in good condition and you can start getting your game on ASAP.

Spentshells - PSUs are rated at widely varying temperatures. Temperature makes a huge difference in what electronics are capable of.

In this case, if you rate the same PSU both in Antarctica and in the Sahara desert, the max wattage that can be pulled from the device will be wildly different. Say a company really does that, which value should they put on the box?

If they were an unscrupulous brand, they would put the numbers from Antarctica to give customers an idea of the *best case scenario*. If they were a solid brand, they would put the Sahara numbers on there to give customers an idea of the worst case scenario.

That is part of why some PSUs that say they can do 700w can really only do 400w in real world conditions and why a lot of them that say they can do 650w can actually do more like 800w+ in real world conditions.

Additionally, the very act of drawing power from a PSU creates heat inside of it. This is where efficiency comes into play. If a 400w is pulling 500w from the wall, that extra 100w is turned into heat inside the PSU casing, serving to raise the temperatures internal to the PSU.

This piggybacks with the ambient temperature of the room the PSU is in to doubly penalize the maximum wattage. Better quality parts can counteract some of this and they are used by the better quality manufacturers, but they are more expensive too, which is part of why you see two PSUs with the same wattage and vastly different prices at a retailer.

The one with poor quality components has a lower cost of components to recover in the selling price and they can therefore get away with selling it cheaper for the "same wattage".

There are tons of PSUs out there with conservatively labeled (at least) wattage. Pretty much every PSU made by Seasonic can power at max load more than what was specified on the box it came in.

I can provide dozens of links from trustworthy review sites like Hardware Secrets and JohnnyGuru to confirm this.
a b ) Power supply
September 17, 2012 9:24:53 PM

Raiddinn said:
Grats, hope everything arrives in good condition and you can start getting your game on ASAP.

Spentshells - PSUs are rated at widely varying temperatures. Temperature makes a huge difference in what electronics are capable of.

In this case, if you rate the same PSU both in Antarctica and in the Sahara desert, the max wattage that can be pulled from the device will be wildly different. Say a company really does that, which value should they put on the box?

If they were an unscrupulous brand, they would put the numbers from Antarctica to give customers an idea of the *best case scenario*. If they were a solid brand, they would put the Sahara numbers on there to give customers an idea of the worst case scenario.

That is part of why some PSUs that say they can do 700w can really only do 400w in real world conditions and why a lot of them that say they can do 650w can actually do more like 800w+ in real world conditions.

Additionally, the very act of drawing power from a PSU creates heat inside of it. This is where efficiency comes into play. If a 400w is pulling 500w from the wall, that extra 100w is turned into heat inside the PSU casing, serving to raise the temperatures internal to the PSU.

This piggybacks with the ambient temperature of the room the PSU is in to doubly penalize the maximum wattage. Better quality parts can counteract some of this and they are used by the better quality manufacturers, but they are more expensive too, which is part of why you see two PSUs with the same wattage and vastly different prices at a retailer.

The one with poor quality components has a lower cost of components to recover in the selling price and they can therefore get away with selling it cheaper for the "same wattage".

There are tons of PSUs out there with conservatively labeled (at least) wattage. Pretty much every PSU made by Seasonic can power at max load more than what was specified on the box it came in.

I can provide dozens of links from trustworthy review sites like Hardware Secrets and JohnnyGuru to confirm this.


http://www.coolermaster.com/product.php?product_id=5888

go on..............
September 17, 2012 9:26:17 PM

Crap power supplies may catch fire trying to deliver 50-67% of rated wattage, but even a crap psu will deliver
under 50% of its rated wattage. You could have gone with a much cheaper corsair or xfx psu (pcpartpicker.com)
that would have had more than enough juice for your build and decent quality too(antec and seasonic are good,
but many antec supplies have split rails that may need to be balanced and seasonic is overpriced).

A i7 3770(77w) and gtx660(150w) will be the vast majority of system draw in a game(227w). Even a corsair
cx430(+12v x 28A=336w) would have been plenty for your build(I'd have suggested xfx 450 or 550 though).
Working(more stress on cpu), the gpu's core and memory will be heavily downclocked, using far less power.

And of course, your 700w cit psu with 2 +12v rails providing 21A each(504w total and more than twice what
you system will ever pull at once)would be totally fine. Waste money if you want(cash better spent on an ssd imho).

a b ) Power supply
September 17, 2012 9:33:56 PM

nukemaster said:
kajabla is right about 80+. Its all about power efficiency and less power waste(HEAT).

A 60% efficient power supply will still deliver its rated wattage. It will just push more heat as well. This said power supplies are rated in DC voltage not AC voltage.

Since the power supply is question lacks the combined 12 volt current, i have to resort to taking everything off too see the minimum amount that can remain.

700 watts total
95.7 watts on 3.3(3.3 x 29)
160 watts on 4 (5 x 32)
3.6 watts on -12(0.3 x 12)
12.5 on 5v standby(2.5 x 5)
271.8 watts used
428.2 left or a bit over 35 amps. is the MIN that this power supply should be able to deliver.

The problem here is that this is very hit and miss since the designer of this power supply may have shared the 3.3 + 5 volt rails leaving more 12 volt current left, but without proper numbers this is my best guess.

Modern power supplies have one huge 12 volt rail and get the others from it. This is how you can now get a 700 watt power supply with 680watts @ 12 volts. This all assumes that the 3.3 and 5 volt usage is kept to a minimum. As the 3.3 and 5 volt use increases it does cannibalize the large 12 volt rail.

From a pure power point, i would guess it would work, BUT from a quality point of view I have some fear for your system.

That corsair unit you posted(CX 750) was FAR better and offers 744 watts(3.3/5 volt rail use allowing) on its 12 volt rail(That runs your system with tons of spare power for anything you toss in down the line).


MAN do you read reviews ? Half and seriously half of cooler master units BOUGHT seem to be able to match the claims. And then you get into what the OP has and what I have powering my media PC HEC 585 rated in review able to maintain 450 watts before exploding (obviously I only mean the caps)


EDIT BOUGHT NOT ALL CM PSU's ARE CRAP.
September 17, 2012 10:02:11 PM

Hey Rich, what all did you have loaded on that cit 700w psu in your old build?
a b ) Power supply
September 17, 2012 10:04:17 PM

Not sure what you are trying to say by showing me a link of a CM extreme power plus 550w.

It is a decent PSU as long as you don't mind ripple up the yin yang and not being able to pull the labeled wattage from the PSU.

I wouldn't use it myself, but it isn't the worst sort of PSU one could put in their PC by any stretch.
a b ) Power supply
September 18, 2012 1:54:17 PM

jtenorj said:
Hey Rich, what all did you have loaded on that cit 700w psu in your old build?



This should have been asked as the first question since I have no reference
!