Originally Posted by Blindsay
yeah it does not have the 4 pin motherboard connector. what would happen if i used a modern ATX12V instead of the 1.3? (just curious) and thanks for the suggestion
You run into a phenomenon called "crossloading". ATX PSUs were built to provide 40-50% of their power on the +5V and +3.3V rails. Modern ATX12V PSUs are built to provide 5-15% of their power on the +5V and +3.3V rails.
Highly technical stuff
Cheaper power supplies (<~$75-$100) use a technology called "group regulation" where the +12V and +5V rails share their voltage regulation inductor on the secondary. But since they share that inductor the two rails can influence each other's voltage. Higher load on the +5V causes +5V voltage to drop and +12V voltage to rise, and vice versa. Manufacturers have to assume that the load on those rails will stay in about the same ratio no matter what. So when you go outside that ratio (for instance, 30% +5V on a PSU designed assuming 10% +5V) the voltage on the +12V and +5V go wonky, +12V going high and +5V going low, possibly going out of spec. Also efficiency usually suffers, and sometimes ripple gets out of hand, though this varies from PSU to PSU.
Too high of +12V voltage can damage fan motors or hard drives (possibly causing a head crash), and can damage +12V-based components without VRMs, and can damage the VRMs on the components that do. Too low of +5V on a system with a +5V CPU can cause system instability and can overwork VRMs.
Long story short: using an ATX12V PSU on an ATX system can lead to bad voltage that can damage components. Unless you use a more expensive indy regulated ATX12V PSU that has 150W+ available on the +5V/+3.3V.