Multiple 12v rails?

[tjohoo]

This might seem like a stupid question..

Most powersupplies has multiple 12v rails...12v1, 12v2, 12v3..what does this actually means? Do ttey refer to different "rails" within the psu or is it three differnt cables from the psu to the mainboard?

 

[jonnyGURU]

They refer to separate rails within the PSU.

These separate rails then feed different connectors on the PSU.

Refer to power supply documentation on how the rails are distributed across the connectors as the arrangement tends to vary from power supply to power supply.