Modular power supplies often don't offer a large number of dedicated PCI-E power connectors but have other 6 pin connectors for peripherals and 4x2 connectors intended for CPU's.
My questions are:
1.) If I were to get the correct cable could I re-purpose those peripheral 6-pin connectors for PCI-E/Vid cards?
2.) What about 6pin splitters? If I was going to use lower watt cards like 75 watt, could I get away with splitting the 6 pin connectors two ways?
3.) I'm interested in this Asus B250 board with all the PCI-E slots and it has molex connectors on the board. Does this mean one doesn't need to power the riser directly because it's being done on the board? Or do you need to run power to both the riser and the molex connectors on the board?
Thanks!
1.) Yes. However, you could also consider connecting the factory modular cables to the PSU (4-pin molex and/or SATA) and use adapters for 6-pin PCIe power. (Avoid running more than 1, maybe 2 per line.) I highly doubt you'd be able to obtain a cable from a reputable manufacturer that goes directly from the proprietary 6-pin connection on the PSU end, directly to 6-pin PCIe.
You could, however, create your own, but you would need to find a pinout diagram or map them out yourself, and ignore 5V and 3.3V outputs. Do note that the proprietary 6-pin connector for peripheral/SATA connections has fewer 12V lines than the dedicated VGA and EPS12V connectors, and thus shouldn't be relied on to provide similar power. Again, limit yourself to 1x 8-pin or 2x 6-pin PCIe connectors.
2.) Most PCIe power cables include either dual 6(+2)-pin connectors, or one 6(+2) and one 6-pin connector. The cable should be fine handling the load of 3x 6-pin connections, should you use one splitter per line.
3.) You should not need to use those supplementary power connections to the motherboard if you are using powered risers. However, whether or not you can use the motherboard connections and use your risers as unpowered risers depends on the design of the specific risers. Back around 2012-2013, some ribbon-style risers could be used as unpowered risers by ignoring the riser's 4-pin molex connector. However, other risers may sever a connection between the PCIe x16 slot and the PCIe x1 connector when connecting the alternate source of power (drawn directly from the PSU, rather than being drawn through the slots on the motherboard).
