At some level, the components chosen for specific PCs follow from standard interfaces, which gradually evolve over time to accommodate ever-changing technologies. Thus, in February 2003, the primary power connector for PC motherboards was extended by 4 pins, from 20 to 24. This was necessary to provide sufficient power for PCIe graphics cards, which can draw as much as 75 W through the motherboard. In addition, more powerful PCIe graphics cards can draw still more power directly from the power supply through a secondary 6-pin cable. An everyday example occurs in high-end graphics cards such as the Nvidia 8800 or ATI/AMD 2900 series.
This 24-pin connector delivers power to modern PC motherboards.
This six-pin connector delivers additional power to PCIe cards.
These soldered pins on the right-hand side attach to leads for power delivered directly from the PSU.
Thanks to the proliferation of Serial ATA (SATA) hard disks, the number of Molex connectors in modern PSUs has been reduced. These connectors are normally designated as part number 0015244048, but are also identified in the ATX12V Power Design Guide as 8981-04P. These wide, four-pin Molex connectors do continue to still be used to deliver power to UltraATA hard disks and other drives as well (primarily, DVD and CD burners or players).
Power connectors for ATA devices such as CD players and hard disks.
A SATA power connector