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Corsair HX750 PSU & MSI MEG b550 Unify Motherboard - not enough 8 pin power connectors

I got convinced on this forum to go for a B550 motherboard over x570, and got the recommended MSI MEG B550 Unify (instead of the Tomahawk X570) - saving a cool £10 for the "cheaper" B550 motherboard.

 

As I installed the Meg B550 Unify motherboard I realised that my Corsair HX750 psu doesn't have enough PCI-E power connectors for this board!  The HX750 only has 4 x PCI-E (6+2, 4+4 CPU) connectors, alongside 6 x Peripheral/SATA connectors, and the 24 pin ATX connector.

 

The MEG B550 Unify motherboard has the 24 ATX connector (ATX_PWR1), 2 x 8 pin PCI-E connectors (CPU_PWR1 & CPU_PWR2), 1 x 6 pin PCI-E connector PCIE_PWR1 

My Asus RTX3070 needs 2 x 8 pin PCI-E connectors, which means I am I x 8 pin PCI-E connector short on my HX750 PSU.....

 

By calculations I only need about 500 - 550 watts, which I thought my hx750 was plenty, but now I don't have enough power connectors on my PSU for the B550 MEG - ironically the 850 watt psu's has 5 x PCI-E/CPU connectors. (Now the B550 is cheaper does not sound like such a valid argument anymore, as I have to spend another couple of hundred £'s for a 850 watt PSU which has 5 x 8 pin PCI-E connectors)

 

What do I do now, return the B550 motherboard, and order the x570 tomahawk (as it needs only 2 x 8 pin power connectors), or spend another whack of money on a new psu (when my hx750 was not cheap and is only about 12 months old).  Does anyone have any ideas or workarounds?

 

In the mean time I have connected my RTX3070's 2 x 8 pin power connectors on the same cable (which is not recommended)

 

 

 

 

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First off, the motherboard doesn't have two 8-pin PCIe.  It has two 8-pin EPS12V.  Depending on what CPU you're using, you only need one 8-pin plugged in.

 

Secondly, you don't need to plug the 6-pin PCIe into the motherboard.  

 

The motherboard is scalable for using parts that need more power than what you need.  Not populating every single connector is not going to make the board not work for a lower power requirement system.

 

You can plug two separate PCIe cables into your 3070 and one 8-pin EPS12V into your motherboard and everything is going to work fine and you have room on the PSU for one more cable if you are inclined to use it for whatever reason.

 

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15 hours ago, jonnyGURU said:

First off, the motherboard doesn't have two 8-pin PCIe.  It has two 8-pin EPS12V.  Depending on what CPU you're using, you only need one 8-pin plugged in.

 

Secondly, you don't need to plug the 6-pin PCIe into the motherboard.  

 

The motherboard is scalable for using parts that need more power than what you need.  Not populating every single connector is not going to make the board not work for a lower power requirement system.

 

You can plug two separate PCIe cables into your 3070 and one 8-pin EPS12V into your motherboard and everything is going to work fine and you have room on the PSU for one more cable if you are inclined to use it for whatever reason.

 

Thank you for replying,

 

I currently have a Ryzen 7 5800x, but plan to upgrade to the 5900x as soon as they become more available and the silly prices drop.  The reason this board looked great to me was  that it has four m.2 drive slots,  and I intend to fill these up over time as I find them on a great deal.  Currently I have a 1TB 980 Pro installed (and have a second 512MB one i will move from my other pc)

 

Do you think that with a Ryzen 9 5900x CPU, 4 nvme drives, and RTX3070 -  that I don't need the second 8 pin CPU_PWR2 & the PCIE_PWR1 to be connected and connect two separate PCIe cables into the RTX3070, and it should be ok with the hx750 psu?  (I've tried to check the msi website & Manual, but but there is very little info to guide you on when to use CPU_PWR2 & PCIE_PWR1 it just says plug it in)

 

Thanks for the help

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4 hours ago, XTPCGuy said:

Thank you for replying,

 

I currently have a Ryzen 7 5800x, but plan to upgrade to the 5900x as soon as they become more available and the silly prices drop.  The reason this board looked great to me was  that it has four m.2 drive slots,  and I intend to fill these up over time as I find them on a great deal.  Currently I have a 1TB 980 Pro installed (and have a second 512MB one i will move from my other pc)

 

Do you think that with a Ryzen 9 5900x CPU, 4 nvme drives, and RTX3070 -  that I don't need the second 8 pin CPU_PWR2 & the PCIE_PWR1 to be connected and connect two separate PCIe cables into the RTX3070, and it should be ok with the hx750 psu?  (I've tried to check the msi website & Manual, but but there is very little info to guide you on when to use CPU_PWR2 & PCIE_PWR1 it just says plug it in)

 

Thanks for the help

You still do not need all of the extra power connectors.  If you actually DID need to populate all of those connections, a 750W PSU would not be enough.

 

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4 hours ago, jonnyGURU said:

You still do not need all of the extra power connectors.  If you actually DID need to populate all of those connections, a 750W PSU would not be enough.

 

 

4 hours ago, jonnyGURU said:

You still do not need all of the extra power connectors.  If you actually DID need to populate all of those connections, a 750W PSU would not be enough.

 

How would someone know/work out when you would need to populate all the power connections on the B550 unify?  

 

I've been scanning the web to get a better understanding of this board and what it can do (call it curiosity & enjoying tinkering with tech) - I know it works without plugging in PCIE_PWR1 (I am using it), but when would I need to use the extra connections? I've not been able find find an answer on when would you need to plug in PCIE_PWR1 - everyone seems to say you don't need to plug it in, but not when you would need to plug it -  why is it there? When would it need to be plugged in?

 

I was hoping there were some info along the lines of: if you do [x] then you need to plug in CPU_PWR1,  if you do [Y] then you need CPU_PWR1 & CPU_PWR2, and if you do [z] then you need to plug in CPU_PWR1 & CPU_PWR2 & PCIE_PWR1

Do you know how if can find out more?

 

Thanks

 

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5 minutes ago, XTPCGuy said:

 

How would someone know/work out when you would need to populate all the power connections on the B550 unify?  

 

I've been scanning the web to get a better understanding of this board and what it can do (call it curiosity & enjoying tinkering with tech) - I know it works without plugging in PCIE_PWR1 (I am using it), but when would I need to use the extra connections? I've not been able find find an answer on when would you need to plug in PCIE_PWR1 - everyone seems to say you don't need to plug it in, but not when you would need to plug it -  why is it there? When would it need to be plugged in?

 

I was hoping there were some info along the lines of: if you do [x] then you need to plug in CPU_PWR1,  if you do [Y] then you need CPU_PWR1 & CPU_PWR2, and if you do [z] then you need to plug in CPU_PWR1 & CPU_PWR2 & PCIE_PWR1

Do you know how if can find out more?

 

Thanks

 

So, I would use the motherboard's PCIe if I were using a higher power 3090, like an EVGA FTW3, for example.  For the second CPU power connector, you would have to be using something like a Ryzen 9 5950X OC'd to 5 GHz+, but then you would need to use a 1000W PSU.

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20 hours ago, jonnyGURU said:

So, I would use the motherboard's PCIe if I were using a higher power 3090, like an EVGA FTW3, for example.  For the second CPU power connector, you would have to be using something like a Ryzen 9 5950X OC'd to 5 GHz+, but then you would need to use a 1000W PSU.

ok, that makes sense in a way. Thank you

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