PC Upgrade RTX 3090 850W GPU Corsair RM850x PSU. 850W PSU will be enough for GPU Asus ROG Strix RTX 3090 OC 25G.

Corsair RM850X Unboxing

Corsair RM850X Unboxing and close look at the Corsair RM850X specifications and cables included.

Corsair RM850X Unboxing

I bought the RM850X to upgrade from Seasonic Prime 650W PSU to 850W PSU.
Waiting for a new graphics card GPU Asus ROG Strix RTX 3090 OC 25G.

My exising Seasonic Power supply might have worked if I could use 2 or 3 separate PCIe cables but I would have to under-volt the GPU a lot to keep the power consumption low and even then, the 650W Power supply might not work.

Unboxing the Corsair RM850X I discovered that the PSU came with 2 PCIe cables and 3 CPU cables.
It would have been a lot more useful if it had 3 PCIe cables.

I did a bit of research and 2 separate PCIe cables are fine. Using 2 PCIe sockets on the PSU and connecting to RTX 3090 with 3 PCIe 12v power sockets.
I will use one PCIe 12v cable standalone and the second one daisy-chained to be able to use all 3 12V power sockets on the RTX 3090 GPU.
The PCI 5.0 Power adapters for the 600W+ single connector uses 2 PSU sockets also. If you look for it, you will see Corsair sells the Type 5 cable set with the PCIe 5 connector taking power from 2 PSU sockets not 3.

The Corsair RM850X had a strong lacquer or power components glue smell that was very strong and it smelled in the room for 2-3 days while in use. Eventually the smell faded away.
Keep your windows open the first 2-3 days you use this PSU. It smells bad but some people like this power transformer lacquer components smell.

The Corsair RM850X is larger than my old PSU Seasonic Prime Gold 650W.
The case dimensions are the same to be compatible with ATX cases but it’s a few centimeters longer.

Installed it and it’s working perfectly

Corsair RM850X installation

For now I have my existing Asus Dual OC 6G RTX 2060 installed in the PC and my RTX 2060 only needs one PCIe 12V power cable.
I routed the other 2 power cables already waiting patiently next to the gpu for the time to install the new RTX 3090 in there.

Like this, all cables are ready and it will be a quick GPU swap when ready.

I upgraded the PSU also to make sure that I reduce the chances of the RTX 3090 not working and I didn’t want to do the PSU and GPU upgrade together to make sure the PSU works with the existing GPU before upgrading the GPU too.

Doing it in steps to avoid doing too many changes at once in case a component is faulty.

Corsair PCIe Type 4 extra cable

Corsair PCIe Type 4 extra cable installation

PCIe cables are ready to go, PSU works fine with the existing setup. Ready for the Asus ROG Strix OC RTX 3090 24G GPU.


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