Question Power supply cables not fitting the motherboard cpu ATX

[MyFirstAttempt]

Hi, I am building a PC I am using a Z690 DDR5 mother board and a Seasonic Focus GM-750 PSU.
Firstly some of the cables are not marked so I would like some help identifying which is which. Secondly none of the cables on the PSU seem to fit the motherboard. I am adding pictures of the motherboard diagrams and the cables in hope to understand what to do.
Motherboard diagram (page 5) in advance.

 

[--SID--]

The 6+2 pin are PCI-e cables for the GPU.
The 4+4 pin are CPU cables you put in de motherboard in the upper left corner.
Besides that you need a 24 pin ATX cable but as seen on the 2nd picture you already installed it.

 

[MyFirstAttempt]

I am still having a couple of questions:
as seen in the motherboard diagram (user manual linked) for the motherboard: https://download.gigabyte.com/FileList/Manual/mb_manual_z690-gaming-x-series_e.pdf (page 4)
I have two CPU sockets: a 2x2 and a 2x4. Do I only need to plug the 2x4?
Also, the cables just don't fit. the socket is :
Octagonal Square Square Octagonal
Square Octagonal Octagonal Square

the Plug is:
Octagonal Square Octagonal Octagonal
Square Octagonal Octagonal Octagonal

 

[--SID--]

4+4 only is enough.

Why don't the plug fit. An octagonal fits in a square so no issues.

 

[geofelt]

There are two ends to a modular cable.
Seasonic should have the psu end clearly labeled.
DO NOT force anything. Parts are keyed to fit properly only one way.
The cables for the motherboard will be 24pin which I assume you have already figured out.
There is an 8 pin and a 4 pin eps socket on the motherboard.
The 8 pin is probably necessary.
The second 4 pin is there for added power for added pcie cards and overclocking. Most of the time it is not necessary.
But, since you have the cable, use it anyway.
Orient the plugs using the latch.
On the 4+4, just leave the +4 dangling.

Also, if your graphics card needs two power plugs, use a different cable for each.

 

[MyFirstAttempt]

There are two ends to a modular cable.
Seasonic should have the psu end clearly labeled.
DO NOT force anything. Parts are keyed to fit properly only one way.
The cables for the motherboard will be 24pin which I assume you have already figured out.
There is an 8 pin and a 4 pin eps socket on the motherboard.
The 8 pin is probably necessary.
The second 4 pin is there for added power for added pcie cards and overclocking. Most of the time it is not necessary.
But, since you have the cable, use it anyway.
Orient the plugs using the latch.
On the 4+4, just leave the +4 dangling.

Also, if your graphics card needs two power plugs, use a different cable for each.

The PSU is semi modular. The cable does not fit into the socket unless I try to insert an octagonal into a square socket. Which cable I should use? Am I not seeing something? Is my PSU not compatible to the motherboard?

 

[geofelt]

Here is what you should have with your Seasonic GM750 psu:
https://seasonic.com/pub/media/cata...15c2a4b231/f/o/focus-gm-750-accessories_1.jpg
One of the permanently connected cables with a 8 pin connector at the end will be the main motherboard 8 pin eps connector.
In the diagram, there will also be a pcie connector cable which should be labeled pcie.
The connector fits only one way.
The side with the latch on the cable head must match with the motherboard connector side with the latch.