How do I find out which one is my PSU rated wattage?

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panpaper

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There's no sticker on my PSU anywhere, and the product page doesn't say anything about my desktop PC. Digging into the specifications manual, I find this page that gives a few wattage ratings. Which one do I base it on if I want to upgrade my graphics card?

main-qimg-5f995b8073da2b12235948600faed963


Based on PCpartpicker, the configuration I want to use needs about 349W, would I need to worry? If it helps, I live in Canada, and the wall ratings are 120V and 60 Hz

 
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FauxisFox
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FauxisFox

FauxisFox

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So the power rating that you want to consider the maximum is 460 Watts. Here's the detailed explanation: When it says 350 Watts, the PSU manufacturer is claiming that if the PSU is limited to 6 Amperes in input power from the wall, it will only be capable of 350 Watt outputs max. This statement is there only to let you know that if your load is under this reported ceiling of 350 Watts, the PSU will only draw 6 Amperes from the wall at the maximum. If your load is above that, it will switch into 460 watt ceiling mode and draw a max of 8 Amperes from the wall, consuming more power (Watts is amperes times voltage, which in the US & Canada, is about 120 Volts, so a max of 960 Watts from the wall to give your computer 460 Watts of power to its parts). You shouldn't need to worry. Your recommended power ceiling is a good amount below your PSU's max, though in my experience, PC Part Picker isn't that accurate for their estimates. Do you mind sharing the build with us?
 
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FauxisFox

FauxisFox

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No, it's one PSU, different efficiency grades. The max is 460 Watts, but it's the least efficient load level.
 
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TJ Hooker

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How do you figure that? There's no mention of efficiency, other than "Bronze" for one of the 460W entries, which I assume refers to 80+ Bronze efficiency. I would assume that one would be the most efficient, given the other ones make no mention of efficiency.

Also, your previous evaluation of relating output wattage ceilings to input current doesn't really make sense. I've never heard of a PSU having different 'power ceiling modes', and I can't imagine why it would. Plus, the power resulting from 6 or 8 A input current is so much higher than the associated output power (e.g. 6A means at least 600 W input, why would that correspond to 350W output?), it makes no sense to tie the two together.
 
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FauxisFox

FauxisFox

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It's actually perfectly normal. I'll post a picture of a server PSU that I have when I have time. PSU's don't have a single power output. They're variable. They can output power using different internal circuits according to the load placed on it. If they only had one power circuit, it would not scale well to lower power targets and could damage attached parts or feed out poor quality power. Keep in mind that PSU's are no where near 100 percent efficiency on their input power, and not all of the input power is used to reach 350 Watt output. A lot of it is lost as heat, but 6 Amperes is the worst case scenario for quality control. Real world usage will have it drawing power at much lower Amperes, but 6 Amperes is the maximum acceptable current for that circuit.
 
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TJ Hooker

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When talking about consumer, desktop PSUs, they do have multiple power outputs in the sense that they have various voltage rails (e.g. 12V, 5V, etc.), but they don't have different circuits they switch between based on load (well, I guess the +5VSB could be thought of that way, but none of the major rails). Given that, the 'power ceiling modes' don't make sense.

Maybe some server PSUs have additional power delivery circuits, but I would imagine those are for redundancy rather than being reserved for high or low power.

Modern desktop PSUs use a switched mode power supply, which scales fairly well across most of the load range. At the extremes of the rated range performance and efficiency drop, which you can see reflected in the efficiency levels required for 80+ certification. But even a pretty crappy, inefficient PSU (let's say 75% efficient) would only take 470W (~4.3 A @ 110V mains) to output 350W.
 
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FauxisFox

FauxisFox

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Yes, and I agree with all your points (switched instead of unswitched, scaling, etc.), but those points may not apply to the OP's power rating sheet. It looks strikingly similar to a few PSU's that I've seen and had in older servers and desktop workstations. I'll see if I can find any credible sources to prove my argument that the amperage listed are just the maximum currents that the PSU is capable of drawing and that this PSU has different ranges of power delivery, but I guess for now, it would be safer for the OP to assume that the power supply is the lowest maximum wattage.

EDIT: OMG, I feel so stupid right now. Sorry TJ Hooker, I misread the OP's comment about the PSU. I thought that label was on PSU. I had assumed that each portion was a separate circuit for redundancy, like in my Sun Ultra 27 workstation. It's extremely embarrassing; I'm supposed to know this stuff as a computer engineering major. Confirmed, reading carefully is an important skill. I apologize to the OP for any confusion. TJ Hooker is right. The manual is providing three PSU options. That's why each PSU has a different power efficiency rating. To actually determine the likely PSU, the OP needs to provide the computer model number. If the you, the OP is unsure, you can give the CPU and the original GPU and the desktop brand and we can guess from there.
 
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panpaper

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Wow, thank you guys for the responses. Sorry I didn't provide enough information, I didn't know what was relevant and what was not. The desktop I'm using is a Dell XPS 8910. As far as checkout options go, I could choose a CPU, GPU, RAM, and storage, but there was no option for power supply.

The original configuration:

  • i7-6700
    RX 480
    1x 16 GB RAM
    2TB HDD, 7200 RPM
    DVD bay

I've since added a 250 GB SSD for the OS, and my next upgrade would be to replace the RX 480 with a GTX 1080. Based on PCpartpicker, components with similar specs would use 319W for RX 480, and 349W for GTX 1080. If it helps, GTX 1080 was also one of the options during checkout, but I couldn't afford it at that time.

Looking up my service tag on Dell.ca returned an itemized list of components. There was no PSU listed, but there was one part that said "Regulatory Label", with the description "LABEL, REGULATORY, EXTREME PERFORMANCE SYSTEM, JSD2, 8910, 460W, FLEXIBLE PRINTED CIRCUIT". I would assume that was it, but I really don't know anything about power supplies, so I thought I'd get some expert opinion here.

If it's not too much trouble, could anyone try to explain everything that was said in simpler terms? I imagine it would help other users too. Thanks a lot!
 
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FauxisFox

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So it appears that Dell installed one of the two 460 Watt options into your desktop. It says nothing about 80+ Bronze, so I assume it's the APFC one. Honestly, if you haven't made any changes to your GPU or CPU, the stock PSU should serve just fine (unless it has done some crackling and smoking recently, in which case, do look for an exact replacement from Dell or their OEM). 460 Watts makes sense given that the power bill looks like:

i7-6700 ~65 Watts
RX480 ~150+ Watts (They tend to exceed TDP, so just to be safe, I'll say 170 Watts unless Dell put a physical power limit)
1x16GB Ram ~5 - 10 Watts
2TB HDD, 7200 RPM ~10 - 15 Watts
DVD bay ~0 - 15 Watts

This totals to around 275 Watts for components, plus 25 - 30 Watts for the motherboard and its USB headers, so the estimated power requirement for your stock desktop should be around 315 Watts (PC Part Picker's pretty accurate with the TDP estimation, but not the recommendation), so 460 Watts is a pretty decent/safe as the max load of your PSU.

The RX480 has around the same power consumption as the 1080. The 1080 is officially rated at 180 Watts compared to the RX's 150 Watts, and in practice, will consume power within 30 Watts of each other under maximum load.

You can check out a test system here:

http://www.anandtech.com/show/10325/the-nvidia-geforce-gtx-1080-and-1070-founders-edition-review/30

The specs of their machine is here:

CPU: Intel Core i7-4960X @ 4.2GHz ~130 Watt TDP
Motherboard: ASRock Fatal1ty X79 Professional ~25 - 30 Watts
Power Supply: Corsair AX1200i
Hard Disk: Samsung SSD 840 EVO (750GB) ~5 - 10 Watts
Memory: G.Skill RipjawZ DDR3-1866 4 x 8GB (9-10-9-26) ~20 ~ 40 Watts

So their base system can be estimated to consume 210 Watts under load. Your desktop without a GPU will consume around 145 Watts. Their own numbers are a good distance from 460 Watts, so you really should be fine with the SSD and GPU upgrade. An extra SSD will only add about 5 to 10 more Watts, but on a power budget of 345 Watts with a 1080, using 355 Watts against a power maximum of 460 Watts will be perfect.
 
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omargodinez61

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Fauxisfox, this completely off topic, but I saw you have an ultra 27. I saw one for sale for $200. I am trying to find a cheap option to experiment with compromising(ethereum). Do yo think this is good option to experiment with?
 
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