Power allocation to various components


Standard Member
I have an old ATX PSU with just 4.2A on the 12V rail. Everything else is fine as it totals 145W.

I don't want to replace it for a newer, P4 compatible one because I am building a low power system and the PSU's consumption at 10% load (on a 400W, £10, PSU) will probably be around 30W. If I blow this one that is an option as it should at least support any new fangled standby modes that my one doesn't. I see 400W supplys with just 12A on the 12V rails so I think my ratio (12V rail Vs total Power) should be ok.

Anyone know how much modern mobo's rely on the 12V rail?

I know USB is 5V and intend to utilise it for all but the main 2.5" drive. Am I right to think it's a pretty safe assumption that USB will not need the 12V rail?

Had a look at Conventional PCI - Wikipedia, the free encyclopedia and it would seem PCI's 12V rails are optional, best not to tax the system further with that for now though...

Let me be more specific, I want a G41 chipset (so I can use cheaper DDR3 RAM) and a Celeron E3x00 to hang off this PSU, and perhaps after undervolting that I can carefully add an internal DVD.
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you should be fine as long as you are not using a high power graphics card, as far as 12v goes i believe that sata uses 12v but it can also use 5v and 3.3v forgive me if i'm wrong but thats what i believe to be tru, i also believe that molex runes on 12v so i guess a lot of the pc uses a 12v supply, all you need to know though is that the psu should be fine for what you are doing, i've been running a sempron system on a 350w psu for a couple of years now.

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