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Question AMD Ryzen 5900X CPU Power Connect 8 pin or 8+4 pin use?

candasulas

Junior Member
Sep 30, 2020
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Hello to everyone. I'm using an Asus X570 Crosshair VIII motherboard with a Ryzen 9 5900X processor. My power supply is Corsair RM850X.
My question is;
My motherboard has 8 + 4 CPU power inputs. Would I have a problem if I don't plug in the +4 Pin power jack? I don't want to deal with cable mess. Corsair cables are thick and difficult to bend. Can I use it with only 8 pins without any problems?

I do not overclock my processor. Only PBO is active. In Auto setting.

I would be very happy if you give information.
 

DrMrLordX

Lifer
Apr 27, 2000
16,888
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Didn't we have some circumstances with Matisse systems failing to boot unless all the auxiliary power connecters were populated? That might have been board-specific (and might not even apply to Vermeer) but it's worth remembering . . .
 

scannall

Golden Member
Jan 1, 2012
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Didn't we have some circumstances with Matisse systems failing to boot unless all the auxiliary power connecters were populated? That might have been board-specific (and might not even apply to Vermeer) but it's worth remembering . . .
Yes, some boards worked fine with just the 8 pin, others didn't. Read reviews first I guess.
 
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MrTeal

Diamond Member
Dec 7, 2003
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I always just assumed it was just so that if you had a 4 pin cable you could plug it nicely into the 4 pin instead of occupying half the 8 pin. Even if your CPU drew 400W from the EPS plug, that's still only 8.3A per conductor. My relatively budget X570-P has both and there's no way it would even come close to stressing an 8 pin without blowing up the VRMs.
 

Hitman928

Diamond Member
Apr 15, 2012
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I always just assumed it was just so that if you had a 4 pin cable you could plug it nicely into the 4 pin instead of occupying half the 8 pin. Even if your CPU drew 400W from the EPS plug, that's still only 8.3A per conductor. My relatively budget X570-P has both and there's no way it would even come close to stressing an 8 pin without blowing up the VRMs.
Inexplicably the 4 pin cable had to be plugged in on some boards (as mentioned above), despite the huge electrical margin with just the 8 pin plugged in. If I remember right, at least one of the boards that had this requirement came out with a BIOS update removing this requirement. It seems to be part of the checks of the boot process that all of the power cables were plugged in and it wasn't programmed correctly that the 4 pin was optional, but it's best to check the manual and feedback for the motherboard anyone is looking to purchase if you don't have the extra 4 pin on your PSU.
 
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Kenmitch

Diamond Member
Oct 10, 1999
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If the MB has both I install both. I see no logical reason to not connect it. The what if's out way the extra few minutes/seconds required to connect it. More consistent and possibly cleaner power delivery is my reasoning. It's so much easier to just hook it up during the build. What if you run into issues that you think might be related to the power delivery? Depending on the case/cooler used it can be a pain in the butt to get to that corner of the MB.

Stiff cables that create more clutter? Pick up some 8pin cpu extension cables if it's your only real issue.
 
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MrTeal

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Dec 7, 2003
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Yeah, that would be a crazy requirement given the relatively small number of PSUs that have dual EPS connectors and how many people would be building with 65W CPUs.
 
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blckgrffn

Diamond Member
May 1, 2003
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If the MB has both I install both. I see no logical reason to not connect it. The what if's out way the extra few minutes/seconds required to connect it. More consistent and possibly cleaner power delivery is my reasoning. It's so much easier to just hook it up during the build. What if you run into issues that you think might be related to the power delivery? Depending on the case/cooler used it can be a pain in the butt to get to that corner of the MB.

Stiff cables that create more clutter? Pick up some 8pin cpu extension cables if it's your only real issue.
Lots of PSUs don't have the additional connector though, so it seems like an easy to way to generate confusion, get helpdesk tickets opened, etc. all for what appears to be a largely symbolic inclusion. This thread is a perfect example.

Just sayin' that since it has to cost money for the board makers to add it, what's the point?

I mean really and specifically, what's the benefit that makes it worth the headache?
 
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MrTeal

Diamond Member
Dec 7, 2003
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Depending on how the 8 pin is implemented, if your board required both the 8 pin and 4 pin you might be able to get away with using the first 4 pins of your 4+4 PSU connector in the 4 pin board spot, and then the second +4 pins in the last 4 pins of the 8 pin board connector. That would require the 8 pin to not have individual sensing on different pins of the connector though.
 

Kenmitch

Diamond Member
Oct 10, 1999
8,385
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Lots of PSUs don't have the additional connector though, so it seems like an easy to way to generate confusion, get helpdesk tickets opened, etc. all for what appears to be a largely symbolic inclusion. This thread is a perfect example.

Just sayin' that since it has to cost money for the board makers to add it, what's the point?

I mean really and specifically, what's the benefit that makes it worth the headache?
Choosing a compatible PSU unit should be one of the final decisions when planning a new build. If upgrading a rig the PSU's connectors should be considered when choosing components.

Telling those who ask for advice that it's 100% optional in all scenarios doesn't look to be sound advice.

Connecting both is the safest answer.

Purchasing a PSU with only a 8 pin connector, because you read the 4 pin is optional on the internet, isn't the wisest choice.

From the ROG Crosshair VIII manual:

View attachment 38049
The image doesn't really sway the argument one way or another. If you read the test then a person could come to the conclusion that connecting both may or may not make the MB run cooler. It's more or less a don't ;be an idiot and only connect the 4 pin connector message.
 

blckgrffn

Diamond Member
May 1, 2003
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Choosing a compatible PSU unit should be one of the final decisions when planning a new build. If upgrading a rig the PSU's connectors should be considered when choosing components.

Telling those who ask for advice that it's 100% optional in all scenarios doesn't look to be sound advice.

Connecting both is the safest answer.

Purchasing a PSU with only a 8 pin connector, because you read the 4 pin is optional on the internet, isn't the wisest choice.

The image doesn't really sway the argument one way or another. If you read the test then a person could come to the conclusion that connecting both may or may not make the MB run cooler. It's more or less a don't ;be an idiot and only connect the 4 pin connector message.
I mean, I guess? That's a fairly narrow interpretation, valid only when buying it all at once, I use PSUs all the time that I buy because they are quality and good price, I almost never plan out and execute a full build all at once. Other people upgrade their PCs but don't upgrade their PSUs.

Upgrading your PSU to get a 4 Pin that is essentially cosmetic is pretty... well, that seems like $70-$150 that should be spent on anything else that will make your computer noticeably better.

For the OP specifically, discarding an RM850x because of the lack of secondary 4 pin would be really wasteful, IMO. It also wouldn't shock me that anyone with that kind of PSU would be subject to the nasty surprise of this motherboard requirement a) because it's not something you know to avoid until you are stuck with it and b) you're under the impression that a currently sold, $130 high tier PSU is going to have all the plugs you could possibly need.

I am all for plugging it in if you have the right connectors or avoiding boards with it if you don't, but it seems to me that the motherboard makers are making life more complicated than it needs to be and I don't understand why.
 

Kenmitch

Diamond Member
Oct 10, 1999
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For the OP specifically, discarding an RM850x because of the lack of secondary 4 pin would be really wasteful, IMO.
It would be considering it comes with 2 EPS12V connectors. His only concern looks to be the stiffness of the stock cables and the cluttering. It's the reason why I suggested getting some extensions which will help greatly in the routing and cluttering. Some extensions are even 4+4 configured to cut down more on the clutter.

I have the same PSU in my 5600x/x570/6800 build so can relate to the cable stiffness issue.
 
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blckgrffn

Diamond Member
May 1, 2003
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It would be considering it comes with 2 EPS12V connectors. His only concern looks to be the stiffness of the stock cables and the cluttering. It's the reason why I suggested getting some extensions which will help greatly in the routing and cluttering. Some extensions are even 4+4 configured to cut down more on the clutter.

I have the same PSU in my 5600x/x570/6800 build so can relate to the cable stiffness issue.
Ah, yes, then I definitely agree.
 

KentState

Diamond Member
Oct 19, 2001
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I only used the 8-pin on my Crosshair VIII Formula board which was one of the options according to the manual. I have not had any problems with both a3900XT and 5950X.
 

candasulas

Junior Member
Sep 30, 2020
10
0
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I mean, I guess? That's a fairly narrow interpretation, valid only when buying it all at once, I use PSUs all the time that I buy because they are quality and good price, I almost never plan out and execute a full build all at once. Other people upgrade their PCs but don't upgrade their PSUs.

Upgrading your PSU to get a 4 Pin that is essentially cosmetic is pretty... well, that seems like $70-$150 that should be spent on anything else that will make your computer noticeably better.

For the OP specifically, discarding an RM850x because of the lack of secondary 4 pin would be really wasteful, IMO. It also wouldn't shock me that anyone with that kind of PSU would be subject to the nasty surprise of this motherboard requirement a) because it's not something you know to avoid until you are stuck with it and b) you're under the impression that a currently sold, $130 high tier PSU is going to have all the plugs you could possibly need.

I am all for plugging it in if you have the right connectors or avoiding boards with it if you don't, but it seems to me that the motherboard makers are making life more complicated than it needs to be and I don't understand why.
It can be difficult to pass through and install 2 8pin CPU power cables when configuring the computer. The cables are too thick. I have a Cooler Master H500P Safe. And I have to run the power cables in the back top corner. I don't want it to be messy. So if only one 8 pin power cable is enough, I will not plug in the other.
 

candasulas

Junior Member
Sep 30, 2020
10
0
11
As I learned with my MSI Unify - do what the manual says to do, no what random people on the internet say.
The manual doesn't mention the obligation to wear both.
Install 8 pin cable for CPU power
Or optionally it says plug in 8 + 4 pin cable
 

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