miniITX power supply for ATX motherboard?

uldics · 09-24-2007, 01:11 PM

I am in research of powering my future carPC. Have decided a motherboard to be ATX or at least miniATX. Need a power supply. Inverter is not an option, as it uses up to 25% of delivered energy just to power itself. Best DC-DC power supplies are for miniITX systems. And I want to use miniITX power supply for an ATX motherboard.

So I see that ITX and ATX power plug specifications differ in wires count and also 3V (mITX) or 3.3V(ATX) wires. ITX connector has 2 rows of 10 wires and ATX has 2 rows of 12 wires. So ATX has 4 wires more: +12V, +3.3V, +5V, COM. And ITX doesn't use one wire , where ATX has -12V (strange voltage, if you should ask me).

And my questions are:
1. Can I take +12V from another +12V wire, or they are separately regulated in ATX and would make system unstable or even burn down some part?
2. Does it matter so much if there is +3.3V and I can take +3V instead? Integrated circuits should be same type on both ITX and ATX motherboards, right? So it is maybe just written in specification +3V, but is really meant +3.3V.
3. What is that -12V on an ATX for a wire and can something be done about it?

DarquePervert · 09-24-2007, 01:29 PM

The PSUs are all ATX compliant as far as power goes. Most of the miniITX motherboards have ATX-compliant power controls, as well (not all, mind you!).
There is no such thing as "miniITX power supply" as far as I know (barring the infamous PW200 POS). I'm curious to know what motherboard you're using that has a pinout that differs from ATX standard.

The 24-pin connector that you're specifying is the newest ATX standard. All the DC-DC PSUs sold in the mp3car.com store (as well as other vehicle PC resellers) that are ATX compliant do not provide the newer 24-pin ATX connector, but a 20-pin connector that works just fine with any ATX-compliant motherboard, even the miniITX boards you've looked at.

I think you're worrying over nothing, to be honest.

uldics · 09-26-2007, 11:15 AM

I think, you misunderstood me. I was looking for miniITX power supply, which provides less features (a few wires not in use) to plug to an ATX motherboard, which probably needs those features not provided by miniITX power supplies. If they provide those features, why are they then not called ATX power supplies?

nst6563 · 09-26-2007, 11:45 AM

a 20-pin ATX connector will work in 90% of the ATX motherboards which have a 24-pin ATX socket. The reason for the extra 4 pins in the new ATX spec are to provide extra dedicated power to the PCI-Express slots.

I have 3 desktop ATX boards which have the 24-pin ATX connector on them. 1 DFI ultra-D and 2x Asus A8N32-SLI. I've powered all of them with a 20-pin ATX psu. I've powered the DFI board with my Opus 150 as well which is a 20-pin ATX DC-DC psu.

like DarquePervert said, you're really worrying over nothing. ATX is a standard. Chances are if the PSU you chose says "ATX x.x compliant" then you're safe as long as the psu wattage is within the requirements you need to power your system.

DarquePervert · 09-26-2007, 12:17 PM

Quote: Originally Posted by uldics

I think, you misunderstood me. I was looking for miniITX power supply, which provides less features (a few wires not in use) to plug to an ATX motherboard, which probably needs those features not provided by miniITX power supplies. If they provide those features, why are they then not called ATX power supplies?

Do you have a link to a "miniITX power supply"?
Judging from your post, I don't think you do, and for good reason.

As far as I know, there is no such animal, as there is no miniITX power specification. There is an ATX power specification, which most (not all) of the miniITX motherboards comply with. miniITX is just a formfactor, nothing more.