Hello

I have a test PC whose PSU is pretty noisy. OTOH, I have two PicoPSU available, an 80w and a 90w.

I don't know how to check which of the two, if any, will be enough to power the PC that has the following parts:

• Motherboard Asrock K8NF4G-SATA2
• CPU AMD Sempron 2600+
• 2.5" Samsung HM121HJ hard drive
• PCI telephony card

Incidently, what happens if we use a PSU that doesn't provide enough power to a PC? Will it just not run, or will it fry?

Thank you.

I believe people have complained about slow low grade hard drive corruption that you don't notice until it is too far gone.

I've never heard that before. Seems possible but is it really a real threat?

Thanks for the tip. Is there a document or web application somewhere that I could use to estimate the power requirements for those parts?

When I read it, I wondered the same thing. Who knows, I got it from the internets. It scared the begebees out of me. It maybe so traumatized me that I will forever after make sure I will always have an extra 20 watts of headroom that I might not otherwise insist on. The only way to affirm this is to experiment by putting your data at risk.

My calculations say you need 250 watts at minimum. You can sell one of your picos and buy a reputable low power PSU with the cash.

Too bad :-/ I'll try to find a quiet, regular size PSU, then. Thank you.

I'd get this one: http://www.newegg.com/Product/Product.a ... 6817151086

Another option, which is often good, is to have two of the Picos in the same case. One powers only the video card and the rest is run off of the other. It's a bit pricey, though. But I do hear that there are Pico type PSUs that are in the 200W range.

I would really like to see that calculation.

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The 90w PicoPSU could do it. The Sempron 2600+ has a TDP of 62w, so let's assume it uses 60w if stressed with Furmark. nForce4 is really one of the worst out there, but I still doubt the mainboard will consume a lot more than 20w. That 2.5" drive will add another 5w or so.

You'll obviously need an external power brick that could deliver 90w too, PicoPSUs were often paired with 60w bricks for some reason. And even then, you'll be operating with little headroom. So no guarantees.

Just try it, if the PicoPSU has not enough juice, it will either not boot at all or crash/reboot when it tries to load Windows. (these are the typical scenarios.)

I also disagree with the 250W figure. Many PSU calculators out there would give you a number like that. But that's more of a generic "Look for a PSU in this range" kind of recommendation. Not a real world power requirement. I would think the 90W would be enough. But it will be close. Only way to be sure is to pick up a Kill-A-Watt or something and check the actual power draw. If you do, remember that they report AC wattage. PSUs are rated by DC output. So a 90W picoPSU with at least a 90W brick should be able to draw about 110W AC.

I too have a Sempron 2600+ laying around. Not in use anymore. It's too bad they didn't support Cool'n'Quiet. Then you could probably undervolt and/or set the maximum speed to a little less to make sure the power draw stays reasonable. As it is, it will run at full speed all the time. Unless you're lucky enough that your motherboard supports undervolting or underclocking. Most only went up, not down.

I've had PSUs shut down due to being overpowered. This includes a picoPSU 150. Interestingly enough, that one shut off when plugged into a P3 1GHz PC while a picoPSU 120 worked fine. Most likely due to the fact that the 150 is designed to power modern PCs where most the power is on the 12V rail. The 120 and less can probably actually supply a little more juice to the 5V rail that the P3 uses. But I've never seen any damage to anything by overloading a PSU. A good one will shut down if this happens. Bad PSUs could do all sorts of crazy things of course. We recently has an FSP PSU "pop" on a PC at our office. (Coil fried) The PC obviously shut down. But I plugged in a new PSU and it was working fine. Nice job FSP! It took out the PSU but didn't harm the PC.

This guy was asking a similar question last month and ran his Pico through a power meter this morning; perhaps it will provide insight to your situation.

http://www.silentpcreview.com/forums/viewtopic.php?f=6&t=61678

I was using a Pico-type board and it destroyed several hard drives before I realised it was the problem and went back to a standard PSU. I'd actually needlessly spent a fair bit of money building a new PC by then, as I thought it was the rather old P4 motherboard that was the problem, but then it happened again with the new AM3 board.

Do you believe the problem was the size of the power supply or just a defect in it?

that could also be a side effect of the power from the wall not being um.. clean?

if you ran a UPS or some form of power conditioner i wonder if you'd have the same issue. or did you, and the problems occurred regardless?

Hard to say really. It worked for some time before I started having HD problems, so probably a defect, but I guess that may have been caused by the power draw putting too much stress on it.

I tried a Pico originally but it couldn't provide enough amps on the 3.3v for my DVB-T PCI card, which is why I was chuffed when I found the alternative board with plenty of amps on all the lines (I'd already bought the Dell DA-2 when I got the Pico, so wanted to try and get it all working).

I'm not sure he knows enough to test it properly, but I mean to ask my Dad to take a look at it sometime (he knows a lot more about electronics than I do!) to see if he can identify any fault. Probably not worth the effort though, as I'd probably be too nervous to try it again even if we did find something to fix.

I think that would only be a valid hypothesis if Pico-type boards require a UPS and standard PSU's don't. I've always used surge/spike protectors anyway.

i was basing it more on the part where picopsus pass the 12v through from the adapter, whereas i assume theres going to be a fair bit more regulatory circuitry in a standard psu.

I ran my file server on a picoPSU for quite some time, never had any problems with it. My main system have also been powered by a picoPSU for a long time, no problems what so ever. I have a surge protector for my main system but the power is usually pretty clean over here so I doubt I would have any problems without it.

I plan to use a Electrodacus Winmate for my next build though. Filtering the +12v rail can be a good thing.

edit: With my picoPSUs I always do some work with the cables. I bypass the picoPSU and let the brick feed the 4pin +12v connector directly for example. I also don't use the weak barrel connector. Without modification the +12v drops quite a bit in my experience.

I should have mentioned that I also was taking the +12v directly from the brick (for my P4 and GPU), so there shouldn't have been much strain on my pico-type board.

Dear OP, It should run OK.

I have a very similar system, and it pulls ~60w from the wall full load. And that is a 3000+, and overclocked 11% to 2GHz. And a 3.5" HDD. And remember that an 80W PSU can *output* 80w, not draw 80w from the wall. The only thing that may reduce my power draw compared to yours is that the graphics drivers don't work on windows-7 so it is running off the default windows ones, which don't utilise the thing much. But i don't see the IGP pulling 25W+ and i doubt you are stressing it with gaming either.

These PSU calculators are almost all complete FUD.

Also, you may be interested to know that with a relatively modest heatpipe cooler (i'm using the AC freezer), you can run your system completely fanlessly. I peak out around 60*C, after hours of stress testing.

Yet another thing in your favour, the 2600+, whilst it didn't have CnQ (concensus at the time was it made no difference anyway for it), you *could* undervolt it more. Most could only go do to 1.0v, but those without CnQ could hit 0.8v, and without breaking much of a sweat. This is at least true for the s754 version, i believe the same for AM2. So, it is actually better than the versions which support CnQ.

If you are short of power, you should see the hard drive skipping and powering up/down, and stability issues. If you have neither of them, I doubt you have a power problem.

So, in summary, apart from the slowness, you have a pretty awesome system for a silent PC, and should comfortably work with a picoPSU.

mb2, you reminded me that's exactly what I saw with my system, the HD spinning down and up again and sometimes not spinning up properly at boot.

Stupid me took it to be a HD fault, then a motherboard fault rather than a PSU one, but I've learnt my lesson.

Don't know why it only affected the HD, but as you say, if the OP isn't experiencing any such problems he shouldn't have anything to worry about.