How to: Use one Power Supply to power two motherboards safely - Overclock.net

*CyberDruid* · 08-23-06

How to: use one PSU to power two motherboards.

Why would anyone want to use one PSU to power two motherboards? An example is setting up an efficient Folding Farm, or any special build using two boards where space/heat/power is a concern. And here's how you would do that without risking damage to the equipment.

Although it is possible to make or adapt a 20/24 pin brick by using the lead from a donor PSU, 2 into 1 24 pin splitters are available from various online vendors. I would reccomend spending the money and getting a proper Y connector to avoid the difficulty of unpinning a 24 pin brick (which requires some finesse and patience as well as a system for tracking the leads) and eas of converting the PSU back to "normal" service.

That is what the splitter looks like.There are long ones and short ones... You plug it into the PSU brick and into each motherboard. But you still need to split the 4 pin plug that provides additional voltage to ATX motherboards.

One way to split the 8 into 4 is to make a Y adapter

Here making one up is relativiley simple if you have a special tool which I found several places.
Most better PSUs that would be able to drive a pair of rigs will feature an eight pin output that is adapted into a 4 pin. The 8 pin out features 4 yellow leads and 4 black leads providing 12 volts at the proper amperage to the motherboard. Simply unpin the leads from the 8 pin brick, and using a pair of 4 pin plugs (from a donor PSU and/or from a 4 pin to 8 pin adapter and/or from leftovers from sheathing and/or color-matching a PSU) repin the output as 2 4 pin outs instead of 1 8 pin out.

Here I am robbing the leads from a 20 to 24 pin adapter to make up a 4 pin splitter.

This is the 8 pin to 4 pin adapter that came with the PSU. Note that there are four empty holes--that is where the 4 leads I robbed from the 20-24 adapter will plug in--the male and female ends are readily distinguishable--be sure not to accidentally swap one end for end or the plug will not seat properly (duh).

The colored molex kit I bought for a PSU sheathing project came with extra 4 pin connectors--her I have inserted the leads into it--the other ends will go to the 8 pin end of the splitter.

The pointy ends of the leads go towards the PSU, the square, hollow ends towards the mobo...

The other way is remove the 8 pin connector and attach two 4 pin connectors.

Both motherboards will need at minimum a power switch. Powering up one motherboard will not start the other running--but will supply voltage to the second board, which is evidenced by the HSF firing up. Simply power up one board and then when ready power the other. Shutting down one motherboard does not shut down the other. To completely power down the PSU both motherboard power switches must be activated on after the other. And that's all there is to it.

Hope this helps other mad modders and Folding Fanatics out there!

CyberD

*Chozart* · 08-25-06

Another gem from 'Druids Mad Scientist Lab

**gonX** · 08-25-06

I saw those Molex'es and thought "Well well, if it isn't CyberD"

*CyberDruid* · 08-25-06

Considering that the new generation of CPUs is a lot less power thirsty, the current trend toward enormous PSUs might reverse...leaving lots of cheap huge watt PSUs available for double duty. Using dual core CPUs it is easy to bring 4 folding cores online with a used $30 500 watt PSU. With quad core a reality that could mean running 8 Folding cores from a single PSU...meaning the concerns about power use when setting up a Folding Farm could be obviated by the sharing of some components.