Do I need both the 8 pin and 4 pin cpu power plug for my MSI B450 Pro Carbon?

Question

I have bought a new mainboard, an MSI B450 Gaming Pro Carbon, and to my surprise, it features 12 pins for the cpu power connection.

My power supply, a Pure Power 10 BN274 600 Watt, only features 2 x 4 pins connectors. Luckily, it has cable management, yet before I buy an extra 4- or 8-pin cable, I wonder:

Do I actually need to buy an extra cable to get the board up and running? Would the board run fine just with the 8 ports being plugged in? If so, which one should I chose?

The CPU in question for me is a Ryzen 2700X.

Solution 1

From experience, it suffices to install the 8 pin connector on the left.

The right 4-pin-connector is basically a redundancy that the CPU may draw upon under extreme load most likely only relevant when you do extreme overclocking.

(The board manufacturers most likely also build in some more extra room in case the next CPU generation needs more power.)

So only connect the 2 ports (CPU_PWR_1) on the left, and leave the right one (CPU_PWR_2) empty. If your system won't boot or doesn't run stable, only then you should consider buying the extra cable or upgrading your PSU.

Solution 2

To provide another example per paulgreg's answer, I am currently running a Ryzen 7 3700X with an MSI X570 Gaming PLUS. I just installed everything this morning and have been running benchmarks and stress tests all afternoon. My system is running perfectly stable with only the 8-pin CPU connector.

At this point, I'm inclined to believe everyone that the extra 4-pin connector is only there for redundancy in heavy overclocking.

Solution 3

I’ve bought a Ryzen 3700X (65 watts TDP), a MSI X570-A PRO (with also both connectors) and a Seasonic FOCUS Plus Gold 550 as PSU. As you, I discovered the two CPU connectors on the motherboard and that the PSU only had a single CPU 8 pin (2x4) connector.

I tried with that single connector and the system (Windows 10) froze after several minutes of normal use (CPU was not under stress). My system also hosts a Geforce 1070 and 3 SATA SSDs. It draws around 100~150 watt of power without screen, far from PSU 550 watts maximum power.

I’ve replaced the PSU with my 10 year’s old Corsair HX520 (which had both connectors) and the system is perfectly stable since.

So, at least for Ryzen 3000, I think you need to connect both CPU connectors to avoid Windows 10 freeze.

Also, the MSI x570 A PRO manual (page 32) explicitly says « Important : Make sure that all the power cables are securely connected to a proper ATX power supply to ensure stable operation of the motherboard » on the Power Connectors page

Comments

[zymhan]

In my experience, if you're not supposed to use two power connectors simultaneously, the manufacturer makes this very explicit with a plastic cover and warnings.

[Tim G.]

I don't want to be that guy, but did you read the manual that should have came with the board? I remember reading the manual to find out about this exact situation with my motherboard. You reference the manual here, but what you've said is a general warning that is more or less saying "make sure you plug any cables in all the way." It seems like you've already come to a conclusion but the manual should explicitly tell you the valid configurations. If I remember right, its either the 8-pin, or both the 8-pin and 4-pin. This was with an x370 board however, and things might have changed since.

[paulgreg]

Here’s the source : download.msi.com/archive/mnu_exe/mb/E7C37v3.0.pdf - Page 32

[mikato]

"File not found" on that link. I found this - superuser.com/questions/1379482/… It really doesn't say much on that page. "These connectors allow you to connect an ATX power supply." -- great, they allow you to. So do you have to connect any of them? lol. And "Make sure that all the power cables are securely connected to a proper ATX power supply to ensure stable operation of the motherboard." So I guess all are required? They could word that better.

[mikato]

Actually page 8 shows pictures of all 3 being connected. The wording on page 32 is terrible but I think this indicates that all are required (according to the manual).

[Jcl]

For the record, I have a Ryzen 7 3700X on that exact same board (MSI X570-A-Pro), with a Corsair RM650 PSU, with only the first cpu power header connected, and it works perfectly fine for me (even under load)