The AT PSU have these two P-Connectors that I wish to use for giving the Amiga power. Can they be used, for giving power to the board. (I know that I need to change the plugs that are on them right now for it to work) And if I can use them, do I need to solder all the wires of same colours together in order not to overload something inside the AT-PSU?
Just so I know we're on the same page here, you're talking about repurposing the P8/P9 connectors to power an AMIGA, is this correct?
According to
pinouts.ru the P8 connector is the one you want to use. In this case the only duplicated signal is ground - there are two of them on this connector. I would use one for the AMIGA ground connection, and the other one can connect to the SHIELD.
But I would probably choose to use an IDE power connector instead. The only thing is you'd need to pull the -12V from the P8 connector.