New build CPU power help

session savage

Hi all. 

My son (12) has decided to build his own PC. He saved up all his money for the last couple of years to buy all the parts he needs but I think its going to fall on me to help him build it and I have no idea.

I'm having trouble connecting the CPU power from the power supply (Lian Li SP750) to the motherboard (ROG STRIX B660-A GAMING WIFI D4)

The mother board has an 8 pin EPS power connector and a supplimentary 4 pin EPS power connector. (same arrangement as picture)

However the Lian Li PSU came with a cable that wont fill all those holes. The cable has two 8 pins that slide apart into four 4 pins. (Actual cable in image)

The arrangement of the square pins and bevelled pins do not match at all.

The only way I can fit the cable is putting one part of each in to the motherboard. The parts circled in red will fit into the sockets marked in red but either one will go into either socket. 

Am I correct in assuming that its ok to plug either plug into either socket and ignore the middle 4 pins on the motherboard socket?

Any help is really appreciated. Thanks.

Spear

From reading the manual, the PSU comes with 1 ATX 12V CPU cable. That's the one that does fit that 8 pin socket. Don't confuse that with the 8 pin PCIe ones for use with GPUs.

There isn't a second one with the PSU, so connecting both the 4pin and 8pin CPU power sockets isn't possible. But that's okay, from the motherboard manual, only the 8 pin one is compulsory, you don't need the 4 pin one.

session savage

https://www.boards.ie/discussion/comment/120724711#Comment_120724711

Can you see the pins in the image? It's not really clear but there's no way I can insert them with the same arrangement of square and bevelled pins.

Spear

It's a bit hard to tell, but the pins aren't keyed on the end of that for ATX 12v CPU cable. It has a diagonally opposed and mirrored set of keyed pins. The pattern of the sets of 4 in red should be mirrored on the other side. Where are you based?

Edit: although from the way it's cut, the top left diagonal ones should still fit.

K.O.Kiki

https://www.boards.ie/discussion/2058301213/new-build-cpu-power-help

Lian Li SP750 comes with the following cables:

• ATX 24 Pin - 1x
• EPS (CPU) 12v - split into 8 and 4+4
• PCI-e 6+2 Pin - 2 cables (6+2 x2, 6+2)
• SATA - 1X
• Molex - 1x

You want to connect the EPS 8-Pin and 1 half of the EPS 4+4 pin into the 12V connectors at the top-left of the motherboard.

Graphics card takes the 6+2 connectors, NOT the 8-pin!

edit

Amended comment.

You can also see the cables in TPU review: https://www.techpowerup.com/review/lian-li-sp750-750-w-sfx-psu/2.html

Spear

https://www.boards.ie/discussion/comment/120725214#Comment_120725214

What page lists two separate EPS cables? The one I checked only mentions one:

https://lian-li.com/product/sp750/

session savage

https://www.boards.ie/discussion/comment/120724915#Comment_120724915

Yes this is what's confusing me. The end of my cable is clearly not keyed to match but CPU is printed on the cable.

I'm in tipperary. Half an hour from Clonmel, Thurles, kilkenny

Spear

https://www.boards.ie/discussion/comment/120725684#Comment_120725684

That's a bit too far for me to have a look.

They keying doesn't determine what's delivered by each pin. Al the pins on top row of the EPS 12V CPU cable are ground for example. It looks like they used bevelled ones on the left hand set, and not the strictly required square one. The arrangement of pins on the right hand side should be enough to ensure it only fits one way. But it's the CPU cable, it's still the right one and should fit.

session savage

I think your right. When both 4 pins are clipped together it looks like one half is keyed correctly and the other half is universal. I'm certain it will actually go in to the motherboard. They must have arranged it that way to suit other connections also?

You can see the bottom 4 pins are keyed with the square and beveled pins and the top 4 are all beveled. But the beveled pins will go into the square socket I assume.

PS, thank you for the help. My son was starting to panic.

Spear

Being paranoid about power connections is no bad thing. It's one of the few things that can instantly wipe out a machine if something goes wrong.

All sorted and moving along otherwise?

session savage

Yeah I plugged it in as we discussed above and it went in perfectly. I'm confident it's correct. Everything else went together beautifully.

The only thing that caused some confusion was plugging in the power switch cable from the case into the motherboard. The power switch plug had plus and minus clearly marked but the motherboard manual had the corresponding pins named as PWRBTN# and GND. I assumed the PWRBTN# was + and the GND was -.

We are waiting on the graphics card to arrive then will have everything ready to try booting.

Thanks again