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Seasonic 8 + 4 pin CPU power help

GunJam
Level 7
Hello

I have a seasonic 1250w PSU. It is fully modular

for the CPU socket it has a connector on the PSU side that has 12 pins and occupies all of the PSU side CPU socket...BUT it only has 8 wires going to it and my MOBO is the Hero XI and can support 8 + 4 pin. but the MOBO side is only 8 pin as there are only 8 wires.

I would like to run both but I dont know why this PSU only has 8 wires running to a 12 wire socket.

can a buy a cable that has 12 wires that will work with that MOBO and this PSU?

Thanks
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5 REPLIES 5

mdzcpa
Level 12
On my Seasonic 1000w Platinum, I use two cables. One is an 8 PSU side to 8 connector, the other is an 8 PSU side to a 4+4. I just use one of the 4 connectors.

Arne_Saknussemm
Level 40
Just look at your cables and PSU closely. There will be another CPU part on the PSU and a 4+4 CPU cable. In addition to the main 12 to 8 cable

The PSU might be labeled PCIe/CPU and a separate CPU part

Maybe postt a pic here of the PSU connectors

Korth
Level 14
ATX12V is 4-pin, EPS12V is 4-pin or 8-pin ... many PSUs use "hybrid" 4+4-pin connectors for full compatibility with both form factors, mostly because mobos which only require 4-pin sometimes lack enough physical space to accommodate a larger connector.

If it's a 4+4 variety of connector then the plastic blocks are usually designed to somehow key or interlock with each other, and of course to only plug into the mobo "one way" with correct orientations. (Unless the PSU is very cheap low-end no name junk which fails to even meet basic compliance.)

Read the manual/specs carefully if you can't figure out exactly which output to use, the 12V CPU power output is often purpose-dedicated (on an isolated "rail") for tighter regulation and stability. Better to not just plug any random 12V output into it (even if the modular cables happen to fit) unless your PSU documentation says this feature is specifically supported.

https://forum.digikey.com/t/common-computer-power-supply-connectors/328
"All opinions are not equal. Some are a very great deal more robust, sophisticated and well supported in logic and argument than others." - Douglas Adams

[/Korth]

GunJam
Level 7
77718


77719


After reading the replies and re-visiting this I went back through my Crown Royal bag that comes with all Seasonic PSU and did find the 4 + 4 CPU cable that I think I overlooked initially. Its labeled CPU but is going to feed off the PCI-E rail. It has dual 4 pin connectors which is going get in the way plus whole new cable I have to route with my limited space left on the back of the case. It should work fine its just not ideal.

i guess the issue is im still pissed that Its a 1250w PSU it cost a lot and im suppose to believe that the CPU rail wont support a 150w for a CPU and needs to feed off a second rail? OR it would kill them to include an 8+4 cable that could fit in the CPU socket (PSU side) and fit in the 8 and pin socket (MB side) its a way overkill PSU its safe to assume that anyone buying one would be using it on a MB that supports 8 + 4 power. 😕

Either way I think ive got it figured out thanks for the help!

Arne_Saknussemm
Level 40
There are loads of boards that use 8+4 but 4 pin is separated from 8 pin...and loads of boards that use 8+8 etc so PSU mfrs have to do the split 4+4 cable that way.

Not ideal for the OCD to have that 4 pin dangling in the air but populating all headers is a good idea I think...though if you aren't doing LN2 benching you should be fine with single 8pin...