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Hello, I posted what I thought was a legitimate question on Super User at Why are brownouts so harmful?

It was closed almost immediately as not a real question with the explanation "This is not a discussion site"

I think if it were to be closed it'd be for not computer related, but not for "not a real question." This was also closed by a moderator, without any other community request for the closing(no downvotes or close votes or even comments saying I'm stupid)

Do requests for an explanation not count as a question?

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    That seems like a fair question to me since you were asking about the effect of a brownout on computer hardware.
    – Brandon
    Commented Feb 24, 2010 at 23:07
  • The real thing that bugs me about it is it was immediately mod-closed. There was no community attempt to close it or show it needed to be closed.
    – Earlz
    Commented Feb 24, 2010 at 23:08
  • Perhaps you could increase the emphasis on PSUs? "How can brownouts harm PSUs and how can I protect mine?" or some such... SU mods have become a bit tetchy in response to the endless flood of bad questions posted to the site, so your question might also benefit from a specific example if such a thing can be found...
    – Shog9
    Commented Feb 24, 2010 at 23:09
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    @Shog9, just took your advice, hopefully has a chance of being reopened now..
    – Earlz
    Commented Feb 24, 2010 at 23:14

2 Answers 2

Reset to default
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After reviewing the comments and with the edits made I have re-opened the question. It was moderator flagged and already had 3 re-open votes and would have been open fairly soon. I am not normally online at 1:00am so there was a slight delay in cleaning it up.

As for the reason it was closed. It was not voted closed but moderator flagged. You will not be able to see the moderator flags, and user without the ability to close do flag questions as well. At the time I did agree with the flagged comments.

We have become fairly strict on the level of questions that cover a gray area we allow solely because of the nature of Super User. However I will say that in the last few days I have re-opened quite a few questions, which is a nice change.

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    i think both the initial closing and the reopening of this question were good calls. (the initial close reason wasn't the best choice, IMHO, but otherwise closing was appropriate.) it wasn't until the question was closed that the question went from "what's a brownout" to "why's it bad for computers". so i think the process is working correctly.
    – quack quixote
    Commented Feb 25, 2010 at 0:00
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Unfortunately I am not ensconced in SU enough to know what is and isn't acceptable. Off the cuff I'd say that the question as currently formed is fine. Regardless, I've posted an answer as a comment, and will include it here with additional commentary:

The power supply shall contain protection circuitry such that the application of an input voltage below the minimum specified in Section 3.1, Table 1, shall not cause damage to the power supply.

From section 3.1.3 of Intel's ATX12V power supply design guide - http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf

Power supplies have an input section composed of a bunch of silly circuitry that, at the end of the day, provides about 308 VAC to a transformer, which then powers the regulation and conditioning circuitry. This silly circuitry actually forms the major basis of the regulation circuitry, and if you are using less than the full wattage of the power supply may be able to manage with significant undervoltage conditions without falling out of regulation on the output side.

When a brownout occurs, the powersupply will attempt to deliver the rated current for as long as it can (based on the incoming voltage and current) and if it cannot maintain regulation it'll deassert the Power Good signal going to the motherboard. The motherboard is responsible for deasserting the power on signal going to the supply, and if it does so in time, then the supply will drop all it rails and turn off.

If the motherboard fails to do this, the powersupply should drop its rails when it falls too far out of regulation, but that is not guaranteed, and with low quality power supplies you may find your components and motherboard receiving undervoltage conditions as well.

What happens at that point depends on how robust those components are, but it's generally not a good thing.

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