Over the decades it has evolved from the original PC and AT into ATX ... power supply then they are very robust enclosures. The same goes for the wiring loom of motherboard and disk power ...

The power supply blows air over ... but to place all the connectors directly on the motherboard. Prior to the ATX, only the keyboard connector was attached to the motherboard.

With the ATX standard also came the ATX power supply (PSU), the standard for which ... and the -12V rail made optional. The ATX power connector with the mainboard was increased from 20 to 24 ...