[SOLVED] Can I use a dual 6-pin supply to an 8-pin for secondary CPU power?

[OscarWilde]

I have a 12900k cpu and the CPU power on my Mobo (MSI Tomahawk) requires 2 8 pin connectors to power it.

I've realized I apparently misplaced my second 8-pin that came with my PSU (Corsair RM850x) so I only have one. I've ordered a second 8-pin to 8-pin, but it's going to be a while from Corsair, so I'd rather not wait until it gets here if possible. So I'm looking for something safe in the interim.

So the first CPU power slot is 8-pin to 8-pin proper. I'm wondering if I can 'reverse' one of the dual 8 (6+2) cables and go 6-pin + 6-pin on the PSU to 8-pin on the mobo (in CPU power 2) temporarily.

As I understand it a single 8-pin cable can handle 150w and a 6 pin can handle 75w. So the 2 6-pins would be 75w each into one 8-pin (150w) at the other end?
Obviously 2 proper 8-pin cables are better, but would the supply be enough off the 2 6-pin cables be a 'proper' 150w for the 8-pin at the other end?

To be clear I'm talking about a single cable: 8-pin on one end to dual 6+2 pin on the other. The type you typically run to a GPU. But reversing it so it's supply is the dual 6-pin end, and the CPU end is the 8-pin.
A cable like this, but used 'backward'.

I don't know if "reversing" a PSU cable is possible/ a good idea. Thoughts?

 

[Darkbreeze]

You don't need to use two unless you are seriously overclocking and so far as I am aware there aren't any dual 6 pin PCI to 4+4 pin EPS/CPU adapters, and if there were you wouldn't be wise to use one anyhow. Anything beyond the first 4+4 EPS/CPU power connector is only there for very high end competitive type overclocking. If you are not overclocking to a major degree, simply use a single 4+4 connector and don't worry about the other one. This has been the case for several generations now.

Also, there are no "8 pin" CPU connectors. They are all 4+4 which "snap" in half for older boards that only required a single 4 pin EPS connector.

 

[DSzymborski]

I have a 12900k cpu and the CPU power on my Mobo (MSI Tomahawk) requires 2 8 pin connectors to power it.

I've realized I apparently misplaced my second 8-pin that came with my PSU (Corsair RM850x) so I only have one. I've ordered a second 8-pin to 8-pin, but it's going to be a while from Corsair, so I'd rather not wait until it gets here if possible. So I'm looking for something safe in the interim.

So the first CPU power slot is 8-pin to 8-pin proper. I'm wondering if I can 'reverse' one of the dual 8 (6+2) cables and go 6-pin + 6-pin on the PSU to 8-pin on the mobo (in CPU power 2) temporarily.

As I understand it a single 8-pin cable can handle 150w and a 6 pin can handle 75w. So the 2 6-pins would be 75w each into one 8-pin (150w) at the other end?
Obviously 2 proper 8-pin cables are better, but would the supply be enough off the 2 6-pin cables be a 'proper' 150w for the 8-pin at the other end?

To be clear I'm talking about a single cable: 8-pin on one end to dual 6+2 pin on the other. The type you typically run to a GPU. But reversing it so it's supply is the dual 6-pin end, and the CPU end is the 8-pin.
A cable like this, but used 'backward'.

I don't know if "reversing" a PSU cable is possible/ a good idea. Thoughts?

Avoid using terms like 8-pin to 8-pin; using x-to-x invariably means an adapter not the number of pins on a modular PSU to the number of pins on a component. There are no universal standards for pinouts on the side that goes into the PSU, so the number is effectively meaningless. This may seem like nitpicking, but this is an area in which just plugging in something wrong can end your equipment, so it's very important to make sure everyone's using the same definitions.

What you're suggesting is not a viable solution, even a temporary one.

 

[OscarWilde]

You don't need to use two unless you are seriously overclocking and so far as I am aware there aren't any dual 6 pin PCI to 4+4 pin EPS/CPU adapters, and if there were you wouldn't be wise to use one anyhow. Anything beyond the first 4+4 EPS/CPU power connector is only there for very high end competitive type overclocking. If you are not overclocking to a major degree, simply use a single 4+4 connector and don't worry about the other one. This has been the case for several generations now.

Also, there are no "8 pin" CPU connectors. They are all 4+4 which "snap" in half for older boards that only required a single 4 pin EPS connector.

Interesting, so entirely running off the one 8 (4+4) cable is enough? Will it 'overdraw' into that cable? From what I've seen the 12900k can be up to 230ish watts, so wouldn't that be too much for a single 8? Or is the 12900 without overclocking never going to surpass 150w?

I'm not planning on overclocking (especially before my second 8-pin shows up), so that's enticing. I'll just leave it as a single for now then. Thanks for the info!

 

[OscarWilde]

Avoid using terms like 8-pin to 8-pin; using x-to-x invariably means an adapter not the number of pins on a modular PSU to the number of pins on a component. There are no universal standards for pinouts on the side that goes into the PSU, so the number is effectively meaningless. This may seem like nitpicking, but this is an area in which just plugging in something wrong can end your equipment, so it's very important to make sure everyone's using the same definitions.

What you're suggesting is not a viable solution, even a temporary one.

Hey, I appreciate the clarification. PSU cables especially are not an area I'm super familiar with so my terminology is off. Thanks for the help! Based on the couple replies so far I won't try and odd wizardry with the cables I have.

 

[DSzymborski]

Hey, I appreciate the clarification. PSU cables especially are not an area I'm super familiar with so my terminology is off. Thanks for the help! Based on the couple replies so far I won't try and odd wizardry with the cables I have.

The good news is, as Darkbreeze noted, that you can run everything just fine without the extra power cable. It's pretty much the only place one can usually get away with not filling up the power ports!

 

[Darkbreeze]

Interesting, so entirely running off the one 8 (4+4) cable is enough? Will it 'overdraw' into that cable? From what I've seen the 12900k can be up to 230ish watts, so wouldn't that be too much for a single 8? Or is the 12900 without overclocking never going to surpass 150w?

I'm not planning on overclocking (especially before my second 8-pin shows up), so that's enticing. I'll just leave it as a single for now then. Thanks for the info!

The CPU and associated buses don't get all their power through those EPS cables. Those are AUXILIARY supplemental power. They are necessary these days, but primarily power is supplied through the 24 pin ATX cable. The EPS power is there to satisfy high demand and for overclocking. I've not seen ANY system with ANY CPU have problems running on only the single 4+4 EPS cable unless there were significant overclocking concerns involved with the CPU.