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Comment by eqvinox | Hacker News Reader

Having built a few power management circuits myself: this is not how PSUs degrade, at least not in the first 5 years, and generally not "ever" in most cases.

The PSU (notably in this case the M/B VRM, not the ATX PSU) can't really trigger brownouts. 1.05V is 1.05V, and if asked to do so, the PSU will deliver 1.05V. It will just get hotter while doing so over time (and specifically: capacitors degrading.) The voltage references are quite stable over time, and so are the window comparators that ensure "1.05V" is between, say, 1.035V and 1.065V. (Voltage references have essentially continuous engineering history back to the 50s≈60s, it's a "solved" problem.)

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Varies by brand, some use better parts. I've definitely seen file servers that won't boot after 3 years, then I pull a few drives to lower the power needed and it boots. After another year or two I have to pull more drives.

Even with generously specced power supplies, server class hardware, redundant power supplies, and enough smarts to stage the drive spin ups to avoid a large peak inrush current when 16 drives try to spin up at once.

But GP's explanation still holds. The PSU will give the reference voltage, while being less and less efficient. Unable to deliver proper voltage (because it becomes less efficient with time), will not deliver any, until you remove the drives and it can deliver it? Did I misunderstand something ?

Now I'm thinking of these HPE over-over-over-specced PSUs I run and y'all got me worried.

Sort of. It's not just efficiency that's lost, but peak power. But if peak power was causing the CPU problems it wouldn't get better with a replacement CPU.

Sure power supplies provide accurate power ... till they can't. Unlike peak power that starts to degrade from new, the voltages will hold as long as the PS can manage it.

A bit sardonic, but if peak power is the problem, your PSU better be shutting off, since the alternative is that it'll catch fire at some point. (And it normally will shut off, since it has thermal protections. Those are boolean, not somehow lowering output power.)

And again, the ATX PSU doesn't really matter here, the M/B VRM does. Even if the ATX PSU has a failure mode where it delivers 10V instead of 12V — you can still make 1.05V out of 10V. Decoupling is spread all the way too, so short peaks don't explain a lot either.

Lastly, it's of course possible the VRM is misdesigned. But this issue is seen across mainboards from at least 3 vendors… what is the likelihood of all of them getting it wrong in a very similar way? The primary way for that to happen is if they are all implementing Intel's reference design, in which case it's Intel's fault again anyway and we've looped back to the origin of the discussion…

As for everyone getting the same thing wrong being unlikely, seeing how much 'inspiration' there is in the space, especially anything helping the race to the bottom on price... it's not unseen, as in a whole generation of motherboards caps blowing or leaking, bad TPM implementations... not saying your overall point is wrong but this part I don't know

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