How about this then - Pin 20 (formerly −5 V, white wire) is absent in current power supplies; it was optional in ATX and ATX12V ver. 1.2, and deleted as of ver. 1.3. So it's still on all motherboards in case you are using a power supply unit at or below version 1.2. Believe it or not, some people are still using the older power supply units, not to mention you can still buy psu's in the older versions so the motherboard companies leave the connector in place and active.