CPU Power Connection Requirements for EPYC 7452 (155w)

[IamSpartacus]

I have a AMD EPYC 7452 (155w TDP, configurable up to 180w) paired with an ASRock Rack EPYCD8 motherboard. The motherboard has both an 8 pin and 4 pin cpu power connector. I have not been able to find any definitive answers as to which CPUs (I assume based on TDP) require both the 8 and 4 pin connector or if all CPU's do regardless of their TDP. Does anyone have an insight on this?

 

[Kev]

It’s always unclear on this but it seems like the Tyan boards power different domains within the board. My rule is you can never give it too much power but you can starve the board power hence, draw too much current and potentially burn a wire/connection.if both connectors are truly used for cpu power, the current will be split and lowered on each wire. I believe each wire should not carry more than 3A so each wire should provide a max of 36W.

 

[IamSpartacus]

The reason I'm asking is I need a 4-pin CPU type connector to plug in an 8 disk NVMe cage. I could split the second CPU wire but that will take some work.

 

[ari2asem]

Amazon.com: CPU 8 Pin Splitter ATX CPU 8 Pin Female to Dual 8(4+4) Pin Male EPS 12V for Motherboard Power Adapter Cable Sleeved EPS Y-Splitter 9 inches (Not GPU PCIe Splitter) TeamProfitcom : Electronics

Buy CPU 8 Pin Splitter ATX CPU 8 Pin Female to Dual 8(4+4) Pin Male EPS 12V for Motherboard Power Adapter Cable Sleeved EPS Y-Splitter 9 inches (Not GPU PCIe Splitter) TeamProfitcom: Parallel Cables - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

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Delock Products 83410 Delock Power cable 2 x 4 pin Molex male > 8 pin EPS male 15 cm

www.delock.com

 

[bayleyw]

If you have a modular power supply you can often replace one of the PCIe cables with an additional CPU cable (I know it's possible on the Corsair supplies). It's what I did on my old quad socket to get the ridiculous number of CPU cables needed.

 

[Kev]

You are probably fine if you have the 8-pin, 4 x 12V and 4 x GND. This connector alone will provide 144W of power plus you have a bunch of 12V wires on the ATX 24-pin connector. However, if you connect to the 12V GFX connector for a high power graphics card, I would obviously plug in the extra 4 pin 12V power.

 

[68k-dude]

Hello IamSpartacus o/

This is a hard question to answer because it depends entirely on the quality of the components in the system. Good quality Molex connectors, according to the specification can deliver up to 9Amp per contact when used in a 4x2 plug. Working through for the 8pin gives a theoretical maximum of 432W (4 X 9A X 12V) . Now, this is the max spec for the 8pin so I would be a little cautious of going quite that high. Another limiting factor is the quality of the cables used. Fatter heavier gauge cables can carry more current. The 16AWG (1.5mm^2) will be OK with the maximum for the socket. The thin light gauge 22AWG (0.34mm^2) is about half of the max, maybe 4Amps.


TLDR At worst ≈200W at best ≈400W


Are you going for stock frequency or some hard overclocking?

I've tested some of these Molex connectors and it also depends on age and number of mating cycles.

If you are going to push a lot of power keep an eye on the cable and socket temperatures.

Have fun

-68k