Why aren't PSU pins keyed?

[larrymoencurly]

On ATX and similar PSUs, the mobo and SLi connectors are supposed to be keyed by the shapes of the pins (square or bevel cornered), but in real life the fit is so loose that you can plug the connector in any way you want, including backwards.

 

[Thor]

on most PSU's this isnt the case, on my antec, your lucky to get it in the correct way the fit is so tight, let alone backwards... just a better psu , perhaps, better connectors on the card/mobo. perhaps. a combonation of the 2 mostlikely.

not many people on here complaign about the fit of the molex plugs, so im assumeing this is a isolated case.