700w enough?

[rich32G]

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

 

[Raiddinn]

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.

 

[spentshells]

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.

 

[ram1009]

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.

 

[kajabla]

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/ati-radeon-hd-6970-review/10
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.

 

[Raiddinn]

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.

 

[JamesSneed]

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=Story&reid=261

 

[rich32G]

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.

 

[JamesSneed]

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/dp/B0040N55VW. 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.

 

[rich32G]

is this one any good? http://www.ebuyer.com/393120-corsair-cx-series-cx750-atx-power-supply-750watt-80-plus-bronze-certified-cp-9020015-uk

 

[Raiddinn]

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.

 

[rich32G]

A TX650 from the vendor I use is actually £20 more expensive? That there is the cheapest Corsair PSU they suppy.

 

[Raiddinn]

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.

 

[spentshells]

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/ati-radeon-hd-6970-review/10
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

 

[spentshells]

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 ?

 

[spentshells]

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

 

[Raiddinn]

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

 

[rich32G]

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.

 

[jtenorj]

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

http://www.bit-tech.net/hardware/graphics/2010/12/15/ati-radeon-hd-6970-review/10

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-core-edition-4800mhz-gddr5-28nm-gpu-860mhz-1024-cores-dual-link-dvi-i-hdmi-2x

http://www.overclockers.co.uk/showproduct.php?prodid=GX-052-HS

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_7870_7850_video_card_review/

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-ghz-edition/12

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_660_directcu_ii_video_card_review/

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-660-graphics-card/1

The HD7850 is much cheaper now, faster now with newer drivers, and is highly overclockable.

 

[rich32G]

Well that throws the cat among the pigeons. Just as I think I am sorted, someone does that....lol

 

[jtenorj]

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.)

 

[jtenorj]

Thank goodness I caught you in time!

 

[rich32G]

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.

 

[jtenorj]

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.

 

[nukemaster]

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).