[SOLVED] Does it matter which 4 of the 4+4 pin connector I use to power the CPU power 2?

Octavio10621

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I have Gigabyte P850GM power supply and the motherboard is MSI X570 Tomohawk WiFi. The power supply comes with 2x(4+4 pins). Each its own cord. The motherboard requires an 8 pin connector and a 4 pin connector to power the CPU. I've connected the 8 pin connector. And I'm confused about the 4 pin. Does it matter which half of the 4+4 pin connector I connect to the 4 pins?
 

InvalidError

Titan
Moderator
I just checked all the manuals and it seems like the pins on the bottom half are grounds and the pins on the top half are 12Vs. So, am I right to assume that it doesn't matter which half I choose?
One half of the 4+4 EPS12 connector is a mirror image keying of the other. If you put the two halves from the PSU together, you see the following pattern:

TAB
XOOX
OXXO

X are square-keyed pins, O have clipped corners on their bottom edges, makes them somewhat D-shaped.

If you have only a 4-pin connector, it will be the left half which corresponds to the legacy ATX12V pinout and keying. Only the correct half will fit without a fight.
 

Octavio10621

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I just checked all the manuals and it seems like the pins on the bottom half are grounds and the pins on the top half are 12Vs. So, am I right to assume that it doesn't matter which half I choose?
I know that logic just makes sense and I should mark the question as solved. But, this is my first build and I'm pretty nervous and don't want to mess it up.
 
I just checked all the manuals and it seems like the pins on the bottom half are grounds and the pins on the top half are 12Vs. So, am I right to assume that it doesn't matter which half I choose?
I know that logic just makes sense and I should mark the question as solved. But, this is my first build and I'm pretty nervous and don't want to mess it up.
I assume you mean the 4+4 pin plug on the PSU cable.... just pick the one [that is keyed right] and go. Either [pair] should work but if it doesn't try the other cause you might have a defective cable.

With most any Ryzen CPU all you'd ever need are one 4+4, or 8 pins, max. Even just one 4 pin might suffice as Ryzen's are just that darn efficient. That 8+8 is provided for LN2 overclocking, where they push 16core CPU's towards 6Ghz (higher now?) on much, much higher voltage than you'd ever think to use. Current draw in that case is outrageous, even if just for a few seconds/minutes at max to collect benchmark data and shutdown.

EDIT: yeah... @InvalidError ;s post made me realize my post was confusing as I should have noted to match keying.
 
Last edited:

InvalidError

Titan
Moderator
I just checked all the manuals and it seems like the pins on the bottom half are grounds and the pins on the top half are 12Vs. So, am I right to assume that it doesn't matter which half I choose?
One half of the 4+4 EPS12 connector is a mirror image keying of the other. If you put the two halves from the PSU together, you see the following pattern:

TAB
XOOX
OXXO

X are square-keyed pins, O have clipped corners on their bottom edges, makes them somewhat D-shaped.

If you have only a 4-pin connector, it will be the left half which corresponds to the legacy ATX12V pinout and keying. Only the correct half will fit without a fight.
 

Octavio10621

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May 23, 2019
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One half of the 4+4 EPS12 connector is a mirror image keying of the other. If you put the two halves from the PSU together, you see the following pattern:

TAB
XOOX
OXXO

X are square-keyed pins, O have clipped corners on their bottom edges, makes them somewhat D-shaped.

If you have only a 4-pin connector, it will be the left half which corresponds to the legacy ATX12V pinout and keying. Only the correct half will fit without a fight.
Thank you.
I plugged the left half in and it all works well.

Now, I'm just having issues with the M.2 SSD not being recognised in the BIOS.
SSD: WD Blue 500 GB M.2 non NVME. I actually asked for SN 550 NVME one from WD Blue, but the provides sent this by mistake(The SSD fits snugly, but has 2 notches, while the slot only has one. That one fits perfectly).

But, I assumed it would still work, just for testing purposes, but it didn't. I'm not sure, if the same issue will occur when I replace this for the NVME. I'd appreciate any advice, if you know about that stuff as well.
Thanks again.

PS: The SATA HDD I was gonna use as secondary works fine, if that is relevant.
 

InvalidError

Titan
Moderator
The main NVMe slot (the one near the CPU) probably only supports PCIe since it is connected directly to the CPU and the CPU does not have any on-chip SATA controllers to route those lanes to. As drea suggested, use the other M.2 slot. That one is connected to the chipset and the motherboard manufacturer should have used HSIO lanes that support both PCIe and SATA for it.
 

Octavio10621

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The main NVMe slot (the one near the CPU) probably only supports PCIe since it is connected directly to the CPU and the CPU does not have any on-chip SATA controllers to route those lanes to. As drea suggested, use the other M.2 slot. That one is connected to the chipset and the motherboard manufacturer should have used HSIO lanes that support both PCIe and SATA for it.
Yes. I got a NVMe in exchange for it.
But, I am confused about one thing.
The M.2 drive heatsink has a plastic rubbery thing on the side its supposed to touch the NVMe drive.
picture in link.
View: https://imgur.com/a/Ov94Jxc

Am I or am I not supposed to remove the rubber part? It feels like it could easily come off.
 

InvalidError

Titan
Moderator
Am I or am I not supposed to remove the rubber part? It feels like it could easily come off.
That is a thermal pad and it is there because boards and chips across the board aren't anywhere near perfectly flat and some wouldn't make any contact at all with the heatsink otherwise. The same sort of "rubbery things" are used under GPU heatsinks for RAM and VRM cooling, same for motherboard VRM for those that have VRM heatsinks.
 
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Octavio10621

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That is a thermal pad and it is there because boards and chips across the board aren't anywhere near perfectly flat and some wouldn't make any contact at all with the heatsink otherwise. The same sort of "rubbery things" are used under GPU heatsinks for RAM and VRM cooling, same for motherboard VRM for those that have VRM heatsinks.
Thanks. That seems to be the case. The surface of the thermal pad just looked a little like plastic, so I was confused. Everything works fine now.
 

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