ASRock Z390 Phantom Gaming X - which ATX12v should I use?

Hello.
I'm receiving my new ASRock Z390 Phantom Gaming X mobo in a few days. I have read the manual, and at one point I'm confused. There are 2 ATX 12V Power connectors on this mobo, one with 4 pins and one with 8 pins. My PSU only has an 8 pin ATX 12V. In the manual I read, that I must use the 4 pin ATX (??) But why not use the 8 pin which will fit with the powercord from the PSU?
Here is a picture from the manual:


The 8 pin cord from the PSU can be seperated into 2 x 4 pins, but what is the right installation here?
I'm going to use my 8700K in this.

I don't see anything like that in the manual.

You can use a 4 pin supply (plugged into the correct side of the 8 pin connector), an 8 pin, or an 8 pin plus the secondary 4 pin.

You may also use a 24 pin (best) or 20 pin ATX main power connector.

I'm not sure when you might need to use both 8 and 4 pin connectors. Probably never, even if you heavily overclock the 8700k.

#3 It is on page 27 in the English manual.

And I will of cause also use the 24 pin main power connector.

Yeah, I just looked at the manual for that board and it is a bit confusing. It's a shame there isn't a clearer explanation of why you'd use both connectors, or even what's the difference between the two.

With that, my Gigabyte Z390 Xtreme has two 8-pin connectors and I'm using both. Again, there is no clear explanation on why or why not use both.

My guess, being that this is for the CPU, is the more powerful the CPU, and perhaps overclock capability, the more power required. After all these boards are capable of running some very powerful (power hungry) i9 CPU's. With that, I might suggest you use both connectors as I've done. Or you could try the 8-pin first and go from there. Remember those pins are for the CPU. BTW what CPU are you putting on that board?

Burgurne said:

#3 It is on page 27 in the English manual.

And I will of cause also use the 24 pin main power connector.

That may not be clearly written.

What that entry means is that if your power supply doesn't have an 8 pin power connector, but only a 4 pin one, that 4 pin should be plugged into what appears in the image as the right side (pins 1 and 5) of the 8 pin socket. Not the separate 4 pin socket next to the 8 pin.

Some motherboards come with a plastic plug in the left side of the 8 pin socket, so that you'd insert a 4 pin plug into the proper side of the 8 pin socket without studying the manual. (You'd have to remove that plastic plug to insert an 8 pin connector.)

I'm probably giving too much detail. The motherboard is flexible as to what PSUs can supply it.

The answer is simple. If your PS has a 8 pin connector for CPU, use it on the MB 8 pin connector. If your PS has only a 4 pin connector, use it on the MB 4 pin connector.
To avoid cables heating and bad contacts the yellow cables (+12V) are used in parallel. Same to the black cables (0V - Ground)
The more cables you have on the connector, the less heat is generate and the less the chance to have bad contacts.
My MB has only a 8 pin connector. To connect a 4 pin from the PS to the MB 8 pin, you connect it on the left side pins (3, 4 & 7,8)

Megahertz said:

The answer is simple. If your PS has a 8 pin connector for CPU, use it on the MB 8 pin connector. If your PS has only a 4 pin connector, use it on the MB 4 pin connector.
To avoid cables heating and bad contacts the yellow cables (+12V) are used in parallel. Same to the black cables (0V - Ground)
The more cables you have on the connector, the less heat is generate and the less the chance to have bad contacts.
My MB has only a 8 pin connector. To connect a 4 pin from the PS to the MB 8 pin, you connect it on the left side pins (3, 4 & 7,8)

Please look at the manual page again.

If the PSU has only a 4 pin power plug, it goes into the pins 1-5 side of the 8 pin socket. Not the 4 pin auxiliary socket next to it.

The tab that the plug locks onto is shown on the pin -15 side of the 8 pin socket, which confirms that a 4 pin plug would go on that side.

I can't swear that what you suggest won't work, but what you say is at odds with what the manual states.

Fortunately, as the OP has an 8 pin plug, none of that matters.

Megahertz said:

The answer is simple. If your PS has a 8 pin connector for CPU, use it on the MB 8 pin connector. If your PS has only a 4 pin connector, use it on the MB 4 pin connector.
To avoid cables heating and bad contacts the yellow cables (+12V) are used in parallel. Same to the black cables (0V - Ground)
The more cables you have on the connector, the less heat is generate and the less the chance to have bad contacts.
My MB has only a 8 pin connector. To connect a 4 pin from the PS to the MB 8 pin, you connect it on the left side pins (3, 4 & 7,8)

That's actually not so simple as most modern day power supplies have both a 4 & 8 pin connector. Especially those of the modular design type. Example my EVGA PS. Additionally, some 8-pin cables can be separated into two 4-pin connectors - sort of like the 8-pin GPU cable being able to split into a 6+2 Pin connector.

Regardless, even if one was only to use the 4-pin connector, there's also the possibility that the CPU is not getting enough juice because there's not enough power being supplied by that one 4-pin cable. It also why I asked the OP what CPU they're using. Overclocking could also require more power to the CPU, thus the need for more connections.

As I said, my (high-end) board actually comes with two 8-pin-connectors. And I use both being I'm also running an i9-9900K. So yeah, the answer may not so simple as it could depend on CPU used, and whether or not you plan on overclocking, said CPU.

Burgurne said:

Hello.
I'm receiving my new ASRock Z390 Phantom Gaming X mobo in a few days. I have read the manual, and at one point I'm confused. There are 2 ATX 12V Power connectors on this mobo, one with 4 pins and one with 8 pins. My PSU only has an 8 pin ATX 12V. In the manual I read, that I must use the 4 pin ATX (??) But why not use the 8 pin which will fit with the powercord from the PSU?
Here is a picture from the manual:


The 8 pin cord from the PSU can be seperated into 2 x 4 pins, but what is the right installation here?
I'm going to use my 8700K in this.

sygnus21 said:

That's actually not so simple as most modern day power supplies have both a 4 & 8 pin connector. Especially those of the modular design type. Example my EVGA PS. Additionally, some 8-pin cables can be separated into two 4-pin connectors - sort of like the 8-pin GPU cable being able to split into a 6+2 Pin connector.

Regardless, even if one was only to use the 4-pin connector, there's also the possibility that the CPU is not getting enough juice because there's not enough power being supplied by that one 4-pin cable. It also why I asked the OP what CPU they're using. Overclocking could also require more power to the CPU, thus the need for more connections.

As I said, my (high-end) board actually comes with two 8-pin-connectors. And I use both being I'm also running an i9-9900K. So yeah, the answer may not so simple as it could depend on CPU used, and whether or not you plan on overclocking, said CPU.

I agree that IF the OP PS has 8 and 4 pin, he should use both.
But he wrote it has only 8 pin connector. So he should plug in the PS 8 pin connector on the MB 8 pin connector.