Resolved Standard ATX vs ATX12 Power Supplies

I just swapped my S2440BX Pentium 3 @ 500Mhz MB for a D845WN Pentium 4 @ 2 Ghz MB.
The new MB requires an extra 12 volt input for the Processor which the ATX12 supplies via an extra cable.

My system incorporates 2 standard ATX supplies connected in parallel, so I swapped one of the flat 4 pin molex HD pwr connectors for the square 4 pin connector needed to supply the 12 volts to the processor.

DOESN'T SEEM TO WORK! Can't even get into bios setup. Monitor doesn't even wake up.

The main 20 pin MB pwr connectors are identical so I assume the pin assignments are also the same.

Am I mistaken here?

Are there other differences between these two supplies that I'm not aware of?

If not, I may have a bad MB, in which case I'll need to return it for a replacement, but need to exhaust all other possibilities first.

Thanks for any advice.

 

Could you borrow a power supply from a P4 computer to use for testing?

Connecting PSU's in parallel sounds strange. I might not wonder that it wouldn't work.

 

Very strange - that's exactly why I didn't say anything when I first read this post. You are a brave soul Matt, I'm afraid there is little that I can add to provide any guidance.

I will however say this, seeing as how BeachBeauty "swapped one of the flat 4 pin molex HD pwr connectors for the square 4 pin connector needed to supply the 12 volts to the processor ", this could be problematic. A four pin molex connector includes +12, -12, +5, -5 and a four pin 12V includes only +12 and -12, each done twice. If your "swapped" connector includes anything other than two yellow wires and two black wires, you'll need to fix that too.

Beyond that, lets hope one of these "electronic engineering" guru's comes along and jumps into this thread.

 

The Antec P190 comes to mind, though they are not really (electrically speaking) running in parallel - they just share the load.

 

First, I want to thank everyone for your comments.

And Bill, you are correct. These supplies are configured for load sharing.

And Rockster, fear not, I only tapped the Yellow +12 and Black common leads to supply the voltage to my CPU.

As it turned out the problem was RAM. I tried using the RAM from the S2440BX board and it wasn't fast enough. Replaced it with the proper memory modules and the system booted as it should.

So problem resolved.

Thanks again

 

Thanks for letting us know. I haven't come across a dual/parallel power supply before (I would just use a recommended single supply).