What a Dell tech told me about Power Supplies...not true...right?

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EvanBerrett

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Mar 18, 2013
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So I'm building a simple gaming computer for a friend, and to help him see what he's getting out of it, I wanted to compare it to a retail PC. I chose the Alienware X51 since he was already looking at it. I noticed that it is sold with a 240 Watt or 330 Watt Power supply. I also noticed I could choose a GTX 670 2 GB GDDR5 graphics card to go with it...but the Power supply again only goes up to 330 Watt. This I found strange since the GTX 670 lists a 500 Watt minimum power requirement. Sooo, I chatted with a Dell tech.

The Dell tech said they don't have bigger power supplies and that the 330 Watt would work just fine and the GTX 670 would work at full capacity. This doesn't seem right to me. Is there not a chance that the Graphics card wouldn't even boot up without enough power? Is this Dell tech, and possibly Dell just not aware of this and ripping people off? Is it possible to run the GTX 670 on 330 Watts?
 
Solution
RetiredChief
radiovan – You said “will still be sufficient to run the system with a GTX 670”
I said “Would it work MAYBE, all depends on that +12V rail,”
A little difference between will and maybe.

In the following PSU 101, The Rosewill and the Diablotek would power up and MAY work under load but very likely they would last a week before imploding and possibly taking out MB/CP/Ram and GPU. The Seasonic would be OK. Problem is the Dell would not be the same quality as the Seasonic, but better than the Rosewill & Diablotek.

PSU 101
Could NOT find the listed specs for the 330 Watt Dell PSU.
………………… Rosewill 350W ….. Seasonic 350W ….. Diablotek 320W
3.3 V Rail ………. 92 W …………………….. 39 W ………………….. 50 W
5V rail …………. 175 W...
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cookybiscuit

cookybiscuit

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Check the system isn't paired with a crap weak CPU, 330w is plausible if the CPU had very low draw, not that I'd do it.

Not sure why you wan't to compare a system to an Alienware because its obvious it will cost pretty much twice as much as what you are paying, plus the fact that you can't specify any of the components so it will be loud as hell.
 
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EvanBerrett

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The CPU paired would be the i7-4770, so fairly low power draw, but I'm still skeptical. And this is exactly why I'm comparing :p He had been considering Alienware before so I'm merely showing him why that would be a very bad decision.
 
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vipboy28

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Jan 24, 2007
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That dell rep is not a bright bulb at all. Firstly depending on the system, 330 watts is not enough. While it make me possible to run a 670gtx on 330 watts of power however nothing else will have power to run. Your processor can easily use 110+ Watts of power under load, and would only leave you with 220 watts... Yeah good luck with that. get a 500watt or 750 watt PSU. Dont risk it.
 
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Guest

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Although the recommended mimum PSU Wattage for a GTX 670 is 500W, the theoretical power draw of a GTX 670 is 75W (PCIe connector)+75W (6-pin)+75W (6-pin) = 225W. The 225W is assuming you would have the GPU fully loaded at 100%, which unless if you are using it for Folding@Home, run FurMark or the like, is not gonna see that load.

Now, assuming the 330W PSU is 80% efficient, which would give your 264W (theoretical), you will have (264W-225W =) 39W left over to run everything else, if your GPU is seeing 100% load. So unless you have a fully load system where CPU, GPU, RAM and your Storage are running at full load you should be OK running at GTX 670 with a 330W PSU. Depends what your friends plans on doing with the system, I definitely would not be loading it up too much though, and a GTX 670 for browsing the web is a weee bit of an overkill.

Hope this helps.
 
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cookybiscuit

cookybiscuit

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That's not how it works, a 330W PSU can output a 330W, with another 20% energy wasted, so it will pull something like 400W from the wall.
 
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Guest

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Well, I assumed 330W being the power available to the system, from the PSU not the wall. You obviously know better, so please do elaborate on the 400W from the wall, how that will translate to the GTX 670. Looking forward to your explanation. Thanks.
 
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cookybiscuit

cookybiscuit

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You are confusing me. Your first sentence in that last post is correct, your initial description is not. A 330W can provide 330W, it does not use a maximum of 330W and is capable of providing 80% of that. Total system power consumption would include the power wasted by a PSU.
 
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RetiredChief

RetiredChief

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Feb 22, 2007
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1) Power efficiency is a ratio of Power required from "Wall" (Source) compared to what is used by the Load. For example If PSU delievered say 300 watts to Computer and you measured at the wall you would get 375 W 300/375 = .8
It's very hard to draw the MAX from a PSU and that is the reason I used 300 W for Load. But if 330 watts was delievered to the load then cookybiscuit is correct. 330 Watts/.8 = 412.5 Watts from VEPCO (O VEPCO is Va Power Company) and 412.5 Watts is what you pay for.

2. "Yeah good luck with that. get a 500watt or 750 watt PSU" While 750 W is OK it would NOT be the Ideal choice Unless SLI is considered in the future.

3. Recommended Wattages from GPU manuf are based on, IF the User has a Crappy PSU that only deleivers 60% power after it has been on for 30 Min (Temperature deregulation). GOOD PSU are rated for full power output up to a operating temp of 40/50 C.

4. You have to be MORE concerned with the Rating for the +12V rail than the total wattage rating for the PSU!!!!

5. Total System power for GTX 670 (Ref: http://www.anandtech.com/show/5818/nvidia-geforce-gtx-670-review-feat-evga/17 )
Idle About 112 Watts, Loaded running Metro 2033 = 317 Watts. Users system would be less probably closer to 275 Watts max.

Would I use a dinky 330 Watt PSU Not Only NO but HEL* NO - Would it work MAYBE, all depends on that +12V rail, BUT then for How long is also a good question. That is to close to max. A quality 430->450 would be a good choice. 500 Watt would be Max UNLESS planning on SLI in future - you would be dropping below the 20% loading when at Idle with single GPU.

Added "power draw of a GTX 670 is 75W (PCIe connector)+75W (6-pin)+75W (6-pin) = 225W" - That may be the max spec for PCI-e slot and for PCI Connectors, But that does not equate to max power draw of the card. GTX-670 has a TDP of only 171 Watts with a target of 141 Watts.
 
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Guest

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My bad on the confusion. Thanks for clarifying/correcting.
 
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Guest

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Right, the whole point (which you made quite well) was that the 330W PSU (though not recommended) will still be sufficient to run the system with a GTX 670. So the Dell CS was not full of poo.
 
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RetiredChief

RetiredChief

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Feb 22, 2007
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radiovan – You said “will still be sufficient to run the system with a GTX 670”
I said “Would it work MAYBE, all depends on that +12V rail,”
A little difference between will and maybe.

In the following PSU 101, The Rosewill and the Diablotek would power up and MAY work under load but very likely they would last a week before imploding and possibly taking out MB/CP/Ram and GPU. The Seasonic would be OK. Problem is the Dell would not be the same quality as the Seasonic, but better than the Rosewill & Diablotek.

PSU 101
Could NOT find the listed specs for the 330 Watt Dell PSU.
………………… Rosewill 350W ….. Seasonic 350W ….. Diablotek 320W
3.3 V Rail ………. 92 W …………………….. 39 W ………………….. 50 W
5V rail …………. 175 W …………………….. 80 W ………………….. 75 W
+12V rail ……. 180 W ……………………. 432 W …………………. 192 W
TOTAL ………... 447 W ……………………. 541 W …………………. 317 W.

1) Rosewill and Diablotex are POOR PSUs while the Seasonic is an excellent PSU (Based on quality of Part). That is that after the PSU has warmed up the Rosewill and the Diablotek will NOT provide Full rated power.

2) NOTE the Disparity of Rated Power vs adding up what each rail can provide. AND the BIG diff in available +12 V wattage.

3) Also Note that while The Seasonic lists a V1 and V2 each with 18 Amps (432 Watts). 432 Watts available on just +12V EXCEEDs max rating of 350W - NO can DO!.
What this means as an example is say you draw 12 Amps (144 Watts) and just as a wag say 50 Watts for the +3.3 and +5 V. 350 Watts – (144+50) = 156, 156/12 = 13Amps NOTE 12 + 13 IS NOT 18A +18A as specs show. Why the disparity, Manuf list the MAX for each rail based on all other rails = ZERO.

Bottom Line, Personnally I would not try, I would upgrade the PSU
 
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Solution
G

Guest

Guest

Yes, thank you, I was wrong, to use that language and about the preceding information. Thank you for enlightening me.
 
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