[SOLVED] CPU only powers on with 8-pin ATX

[atomiczam]

Recently upgraded my PC to a MSI Z390 pro carbon AC with a 9700k processor but the computer only boots when a single 8 pin ATX cable is plugged in, even thought the board also has a 4 pin connector right next to it. If I plug in the 4 pin too the system doesn't boot. I've seen other people have this problem and just left it alone and it works for them but it's my understanding that the 4pin powers a voltage regulator and I'd really like to have that working.

My only thought is it's a modular EVGA power supply that only came with 1 CPU cable so I used a COMeap ATX 8 pin to 4x4 cable instead of an EVGA cable because I just figured a cable is a cable and all the connectors fit. It's a 850w power supply and the two PSU calculators I tried say the system should only pull low 600s so I don't think it's a wattage problem. I've double checked all the connections and they were seated right when I had them plugged.

Any thoughts on what's causing the issue?



Full Specs:
MSI Pro Carbon AC
Intel 9700k
Corsair H60
MSI GTX 1070 x2
Gskill ripsaw DDR4 3000 4g x 4
EVGA Supernova 850

 

[Lutfij]

No the extra 4 pin connector next to the 8pin EPS is to provide supplemental power when you're going to be doing a high overclock. You should be fine with the 8pin populated. On another note, maybe see if another PSU that is reliably built changes your experience when all connections are made. EVGA are notorious for having bad and good units in the same series(don't ask, their QC is all over the place).

How old is the PSU?

 

[atomiczam]

How old is the PSU?

The PSU is about 3 years old. The only other PSU I could test is a 7 year old 1000w Rosewill which I'm actually afraid to plug back in.

 

[atomiczam]

Update:

I took the cable from the top CPU socket and plugged it into the bottom CPU slot on the PSU and it didn't work. Makes me think it's just a dead rail on the PSU. Glad to know as long as I'm not overclocking I don't need the other 4pin but still not thrilled about having a dead rail in my PSU.

 

[NightHawkRMX]

Depending on the model, it may only have one rail. Could be a faulty/burned out modular port

 

[atomiczam]

Depending on the model, it may only have one rail. Could be a faulty/burned out modular port

You're right; after a quick google search EVGA Supernovas are single rail which means the CPU2 socket/port is bad or burnt out but it's the same end result. Not sure if it's manufacture defect or 3 years of wear and tear (seems unlikely on a port that was never used) but I kinda expected better of EVGA.

 

[NightHawkRMX]

Mights still be under warranty. May be worth trying to getting the unit replaced.

Will still work fine without the 4 pin tho.

 

[SamirD]

Mights still be under warranty. May be worth trying to getting the unit replaced.

Will still work fine without the 4 pin tho.

Definitely try the warranty route. I know a lot of their earlier power supplies had bigger warranties than today.