Another neat thing about them is that the PCs are legitimately junk, so you can get them even for free.
|Stolen from PcHub.com|
If you're like me and don't feel like butchering the connector, you'll need a breakout board. The connector is mechanically (!not electrically!) compatible with an 8-pin EPS12V power connector (plug is Molex 39-01-2080, PCB socket is Molex 39-28-1083, terminals are Molex 39-00-0168 and Molex 44476-1111).
The 8-pin PCIe power connector is different with the placement of the square and hexagonal holes and is not mechanically compatible...not like that will stop the 200 pound gorilla from trying to jam it in...
Needles to say that if you plug this (and turn it on) into an EPS12V connector of a working motherboard, you will turn it into a non-working one, as the voltage is inconveniently reversed and the power supply will turn on. Results may vary from nothing at all to a spectacular fire and mini explosions of the caps.
stolen from http://www.playtool.com/pages/psuconnectors/connectors.html#eps8
|24-pin ATX...cut on the red lines...|
stolen from wikipedia
Yep, it's not a true hack unless it involves a hacksaw!
side note - on any newer-ish junk motherboard, I suggest cutting the connector out, as the inner power layers use thicker copper (for heatsinking) and carry away heat from the soldering, making it very difficult.
As said earlier, plugging this PSU here to the MB is also not a good idea, although it should not turn on (results may vary). If the PSU does turn on, it will be short-circuited, if it "wins" over the short (burns through), it will send 12V to a 5V line...
Here's my quick and (really) gritty breakout board.
I kept the +12V rail from being at the edge, as it lowers the chance of an accidental short. The brass washers are actually soldered to the board.