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Psu question regarding ampage

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October 12, 2012 11:06:26 AM

hi all,
may seem like a silly/basic question.

i have a friend that has most of the components to build his system, all he needs is the gpu.

so, the psu he has.

ezcool 650w, yes i know not a very good psu but he is on a budget.

he is looking at getting a radeon hd 7750 or 7770

the question is,

the psu has dual rails, now it states each rail has 20a, 240w on each rail. i wanted to know if their is any way i can find if the rails are separate or combined, for example:

rail v1 for running cpu rail v2 for the 6 pin pci-e connector.

the gpu's he is looking at, the 7750 does not have its own dedicated power ( no 6 pin pci-e connector ) so it draws the power through the mobo.

the 7770 does have its own 6 pin connector but recommended 20a for this gpu which hits the boundary of one of the rails if they work as separate,



i only ever use single rail corsair psu's so never really looking in to dual rail.

any info would be great.

thanks

More about : psu question ampage

a b ) Power supply
October 12, 2012 11:09:44 AM

dual rail is ok but single rail is just simplier. it still works without over loading the rails.

just get a regular xfx 550w for his needs
October 12, 2012 11:22:31 AM

im afraid he already has the psu, otherwise i would of recommended a better manufacturer, i know alot of people use dual rail and i prefer single, but what i need to know/find out - are the rails used together or on their own.

like i stated above if they are used on their own and he gets a hd7750 then it seems that his whole system will be running on the one rail 20a which wont be enough, or even if he gets a 7770 then the pci-e pin if that draws the other 20a still wont be enough, if they run combined then 40a will be fine as the cpu is only a amd 240 running at 65w.

sorry if this is confusing, thanks for the quick reply
Related resources
a b ) Power supply
October 12, 2012 4:58:45 PM

the psu is most likely going to be configured so that the cpu runs on one rail and the GPU on the other. it should be fine
a b ) Power supply
October 12, 2012 6:18:48 PM

Measured power consumption HIS R7770

1.System in IDLE = 156W
2.System Wattage with GPU in FULL Stress = 229W
3.Difference (GPU load) = 73W
4.Add average IDLE wattage ~10W
5.Subjective obtained GPU power consumption = ~ 83 Watts

Or Better yet: http://www.anandtech.com/show/5541/amd-radeon-hd-7750-r...

Should have no problem with PSU even though I'd derate it by 30 % to 40 % (Nornal deregulation for a LOW Quallity PSU as itheats up.

Total system requirements for a 7750 is only about 216 Wats, But that includes the 5 and 3.3 Volt rails). For the 770, total is about 250 Watts, with ONLY about 83 watts (about 7 amps) required from the PCI 6 Pin power connector.

While the PSU is rated at 650 watts, being a low quality PSU it can not provide full power at Operating temps (rating is only good for a temp around 20->25 C. While it should provide plenty of power, the BIGGEST concert would be that it fails and wipes out his MB, CPU, Ram and GPU - that would SURLY KILL his budget.
October 12, 2012 9:13:59 PM

thanks for the replys,

the big troll- if you seem to think that the configuration would be set that one rail would supply to one main component and the second rail to the other main +12v component then it would be better to go for the 7770 as the 7750 does not run off the pci-e connector, is most dual rails configured like this.

chief - thanks for the link and the explanation, you say the biggest concern is if the psu fails, well the only reason i use corsair now is because the my last system was wiped out by an xfx 750 core edition that was only 2 weeks old. the psu managed to arc and the only thing that i could save was the optical drive. i thought xfx was a respectable manufacturer, even after complains i still managed to get nothing from them, not saying that this wont happen with a corsair psu but as yet no problems. in regards to this he has told me what he has brought and i need to work on that, i have warned him that the psu isn't up to much and would be better upgrading it asap.

thank you all for your help, much appreciated
a b ) Power supply
October 12, 2012 11:53:32 PM

you do know that corsair and xfx are just as likely to get bad units? they are made by the same manufacturer and OEM so no reasoning behind that.

it wouldnt matter. they both take power just that one needs a connector and the other one draws most of its power from the pci-e slot which is from either rail
a b ) Power supply
October 13, 2012 3:17:10 AM

Was not refering to a corsair, That is also what I use.
was referring to the ezcool 650w.

a b ) Power supply
October 13, 2012 3:29:04 AM

TheBigTroll said:
you do know that corsair and xfx are just as likely to get bad units? they are made by the same manufacturer and OEM so no reasoning behind that.

it wouldnt matter. they both take power just that one needs a connector and the other one draws most of its power from the pci-e slot which is from either rail


Not necessarily true on the same manufacturer. Seasonic builds only the TXV2, some of the HX, and the AX units (except 1200.. flextronics?) and use different platforms compared to XFX. Corsair CX, GS, TXM units are made by Delta which is a decent enough manufacturer but not necessarily as good as seasonic.


Other than that...

I assume the ezcool is this psu here...

http://www.amazon.co.uk/EZCOOL-650W-24Pin-Super-Silent/...


18 amps on the 12v rail and 33 amps on the 3.3v rail and 38 amps on the 5v rail....

That's barely even a 250/300w psu. I wouldn't even try it mate.

Any decent power supply that's rated "700w" optimistically will have at least 50 amps on the 12v rail.

Or am i looking at the wrong power supply here?
a c 116 ) Power supply
October 13, 2012 5:09:39 AM

lilotimz said:


18 amps on the 12v rail and 33 amps on the 3.3v rail and 38 amps on the 5v rail....

That's barely even a 250/300w psu. I wouldn't even try it mate.


Agreed, those amperages are throwback numbers from days of yore (heavy on 5v & 3v with little to nothing on the 12v rail)
October 13, 2012 8:39:28 AM

the big troll, that's what i was saying that any power supply can go bad, even xfx, corsair ocz.......

chief, i know u was referring to the ezcool.

lil, no its a different psu to the one u listed, i will get him to send the exact details over and post them soon.

thanks for all the replys
a b ) Power supply
October 13, 2012 8:56:09 AM

What a scam. I recommend not plugging that thing in. Ever.
October 13, 2012 12:04:06 PM

well i wouldn't recommend it to anyone or even consider buying it.

the scary thing is tho, the reason he brought this one is because he went to a main pc retailer and they said this is the one that they put in all their systems, maybe a retail pitch but still scary to think of.

unfortunately this is the one he has got to work with and stuck with it, i told him the consequences of having a cheap psu in a system but just don't have the budget to work with now and the mobo he is using dosn't have on-board gpu.
a b ) Power supply
October 13, 2012 12:54:56 PM

I seriously recommend writing that down as a loss and buying a new unit. Learn from the experience. Sucks to lose £30 but too bad.
October 13, 2012 2:01:23 PM

i mentioned about getting a better psu and just picking up a cheap second hand card just for the display for now but its not what he wants to do, its his system, i warned him about the potential loss of the other components if the psu goes so nothing else i can do apart from pass on the info from you guys regarding the psu and gpu at the start of the post.

thanks for all your replys and help
a b ) Power supply
October 13, 2012 7:22:32 PM

38amps on the 3.3v 40A on the 5v, no word on what the combined 12v is. His system will die. I assure you it will. Too bad for him i guess...
a b ) Power supply
October 13, 2012 7:45:39 PM

While the PSU is a LOW quality PSU, and I also recommend changing it.
But to say that it will not power a LOW end LOW wattage GPU.
His Whole system is probably at, or less than, 250W. The 250 watts includes power from ALL rails, all circuits, not just the GPU, but aggree that the majority is from the +12 V railoThe Gpu itself only drays about 85->90 Watts under Load and around 10 watts at idle.

His best choice is accually the 7770 since that would split the GPU wattage between the two rails.

From OP: "he is looking at getting a radeon hd 7750 or 7770"
a b ) Power supply
October 13, 2012 8:00:42 PM

The problem is we have no idea what those "rails" are and no idea of combined output, they could be one 12 V 20 A output simply split into to two with a combined output of less than or equal to 20 A. I wouldn't plug that into a computer.
a b ) Power supply
October 13, 2012 10:41:46 PM

It even avoids saying the combined 12v rails. Furthermore, it even says MAX voltage not CONTINUOUS meaning that it can only output whatever it listed under the most obscure settings.

Low quality 250-300w unit most likely. I feel bad... well not really..
a b ) Power supply
October 14, 2012 3:37:35 PM

3.3 Volt @ 38 Amps = 125 W, for 5 V = 200 watts and for 12 volt = 480 Watts
125 + 200 + 480 = 805 Watts. OPPS max listed wattage for these three rails is ONLY 631 Watts.

TO explain As this is very common in low end PSUs, and to some degree even with Better quality PSUs. Just add up the Individual rails and see if they are at the max PSU rating. Many of the tier one and a good percentage of tier two PSU do provide a more accurate representation of PSU Rails

Each of the rails, IF ALL other rails are suppling zero watts, can supply the rated power at a given temperature. AS I stated for low end PSUs this is normally around 22 C. But as PSU supplies power internal parts heat up - power capability goes down - hense deregulation. For Tier 1 & 2 PSUs output is rated @ 40 C, hense no need to deregulate.
(@ FinneousPJ )
Each ot the two +12 V rails can provide 20 Amps at +12 volts PROVIDING The power provided on the +3,3 Volt Rail and the + 5 V rail do NOT exceed 151 Watts (631 Watts minus the 480 watts = 151 Watts). It is doughtfull his system is drawing over 151 Watts on the +3.3 V & Plus 5V rails.

Bottom Line, for a Low end 7770 system the PSU will provide the needed power- IT'S a CASE of quality, ie the ripple output, noise on rails, and increased probability of a failure.

@ lilotimz "Low quality 250-300w unit most likely. I feel bad... well not really.."
I would say - Low quality 650 Watt that is only capable of suppling about 400->450 Watts.

a b ) Power supply
October 14, 2012 3:45:42 PM

RetiredChief said:

(@ FinneousPJ )
Each ot the two +12 V rails can provide 20 Amps at +12 volts PROVIDING The power provided on the +3,3 Volt Rail and the + 5 V rail do NOT exceed 151 Watts (631 Watts minus the 480 watts = 151 Watts). It is doughtfull his system is drawing over 151 Watts on the +3.3 V & Plus 5V rails.

Bottom Line, for a Low end 7770 system the PSU will provide the needed power- IT'S a CASE of quality, ie the ripple output, noise on rails, and increased probability of a failure.

@ lilotimz "Low quality 250-300w unit most likely. I feel bad... well not really.."
I would say - Low quality 650 Watt that is only capable of suppling about 400->450 Watts.

That's all speculation.
October 14, 2012 4:15:35 PM

well thanks for all the replys, i have convinced him to bet a better psu.

he has given me a budget of £50.

i am having his ezcool to power my old system (amd 64 3200+, 8600gt) if it blows it blows. system was built by scraps.

i was looking at the cx500 corsair, any opinions.

thanks again
October 14, 2012 10:52:44 PM

thanks for the opinion, but in my experience i wont be buying from xfx again.

not just because i had a one fail on me and destroy my whole system due to arcing as this can happen on any power supply, the reason is due to the customer services and technical support.

not sure what it is with most UK sites now not showing the ampage in the specifications, i tend to buy from ebuyer as i have a good account from them.

edit-+12v = 34a
a b ) Power supply
October 14, 2012 10:57:14 PM

Here's some good ones i found on ebuyer UK...

Antec HCG 520 £55.00
http://www.ebuyer.com/245671-antec-520w-high-current-ga...

Antec EA500 £50.51
http://www.ebuyer.com/202319-antec-earthwatts-green-500...

They're decent units and both have better quality than the CX500V2 (which is not bad). Never cheap out on a power supply. If you have a budget for a psu then use as much of the budget as possible on a quality power supply as it'll save you from a lot of headaches.
a c 260 ) Power supply
October 16, 2012 8:19:13 PM

boden08 said:
i mentioned about getting a better psu and just picking up a cheap second hand card just for the display for now but its not what he wants to do, its his system, i warned him about the potential loss of the other components if the psu goes so nothing else i can do apart from pass on the info from you guys regarding the psu and gpu at the start of the post.

thanks for all your replys and help


You can lead him to water, but you can't make him THINK!

Tom
!