I bought an XFX Mercury OC RX 9070 XT, which needs three 6+2-pin PCIe connectors. My current power supply is a Corsair RM750 Gold, but the graphics card recommends an 850W unit, so I purchased a Cooler Master 850W Gold power supply. The Cooler Master includes two PCIe cables: one has a single connector and the other has two connectors on a daisy chain, giving me three connectors total. Can I use the Corsair PCIe cable with the Cooler Master PSU, or is it unsafe? My CPU is a Ryzen 7 7800X3D.
3 Answers
You already have what you need from the Cooler Master unit: two PCIe cables providing three GPU connectors, with one cable using a daisy-chained second connector. That setup is generally fine. Plug the separate cable into one GPU connector and use both ends of the other cable for the remaining two. Use only the cables supplied with the Cooler Master PSU.
Do not mix modular PSU cables between brands or models. The connector may fit, but the pinout on the PSU side is not standardized, so using the Corsair cable with the Cooler Master unit could send the wrong voltage to the GPU or PSU and damage the hardware.
A quality 750W supply may be enough for an RX 9070 XT paired with a 7800X3D, but the manufacturer's 850W recommendation gives you more headroom. You could keep the RM750 if it is in good condition and has the required connectors, or use the new 850W unit. Either way, never add the Corsair cable to the Cooler Master PSU.
I noticed one cable has two connectors and the other has one, so I wanted to confirm that those count as three usable connectors even though there are only two cables.