12V2x6 to 3 x 8 pin pcie cable in reverse.

PeterEv

PeterEv

PeterEv

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Hello,

I would be very grateful for some advice please.

PC spec:
Asus X870 TUF mobo.
Ryzen 7 9800x3d.
MSI MAG A850GL ATX 3.0 psu.
Gigabyte RX 9070 XT Aorus Elite gpu.

The MSI psu 'only' has 4 pcie outputs whereas I need 5, 2 for mobo and 3 for gpu.

I've read that this mobo doesn't really need 2 x pcie + ATX to be safe and whilst I've seen 360W on the gpu, I do wonder if it actually needs 3 x 8 pin pcie although it begs the question why GB made it that way.

The psu does a have a 12V2x6 output so I'm wondering if a 3 x 8pin pcie to +12VHPWR splitter would supply the card, kind of the reverse that a lot of people are using to supply their 40 & 50 series cards from psus without a 12V2x6 output.

*** no competitor links ***

Thanks for any input..

Peter.
 
Last edited by a moderator:
PeterEv said:
The MSI psu 'only' has 4 pcie outputs whereas I need 5, 2 for mobo and 3 for gpu.
Click to expand...
It has 4 outputs:
- 2 will be used for the 2 EPS (4+4) cables for your motherboard
- the other 2 will be used for the 2 PCI-E(6+2 pin) cables, each of which has 2 connectors, for a total of 4 connectors. You will be fine to use 2 connectors from 1 branch, and 1 connector from the other branch.

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Thanks Armageus.

I do wonder why GB used 3 8 pin connectors on this card as surely it'll never ever draw more than 375W even in an extreme overclock.
 
Could be anything from wanting more safety margin for "spikes", to marketing e.g. "our card has 3 which is more powerful", to future reuse of the same PCB for an XTX or other unreleased card.
 
PeterEv said:
Thanks, yes all valid answers..

Out of interest and for a complete solution to get sufficient/surplus supply to the 9070, is there any reason why this wouldn't be suitable?

www.overclockers.co.uk

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Click to expand...

Whilst I'm sure it would work and would likely be ok, personally I don't trust the 12VHPWR connector and wouldn't want to use it - Especially given that you don't need to (as you already have enough connectors on your PSU to populate all 3x PCI-E 8 pin)
 
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Yes, I see a lot of negativity and suspicion about the 12VHPWR connector although most of that I think relates to high power cards that draw near to the max current/power rating of it, e.g. 5090s, etc.

I freely admit to be anal about cabling hence me already cutting off (and sealing) the pigtails to the 3 8 pin gpu cables so I'll order another 8 pin pigtail and use that with a single 8 pin for the gpu.

Since getting the 9070 on Tuesday I have been running with 3 x 8 pin cables to the gpu and only one 8 pin (ATX) to the mobo without issue but it's not sitting right with me.

Thanks again for your help, it's much appreciated.
 
So after an hour of BO6 running FRS4 Ultra settings 1440p 150+ fps, assuming HWMonitor is accurate, the 9070 XT TBP hit 411W. That's making me nervous supplying the card only with 1 x 8pin and 1 x 8pin with pigtail..

Given the 9800x3d is so frugal, do you think it might be safer to use 1 x 8pin (& ATX) for the mobo and use 3 x 8pin for the card?

Thanks.
 
PeterEv said:
So after an hour of BO6 running FRS4 Ultra settings 1440p 150+ fps, assuming HWMonitor is accurate, the 9070 XT TBP hit 411W. That's making me nervous supplying the card only with 1 x 8pin and 1 x 8pin with pigtail..

Given the 9800x3d is so frugal, do you think it might be safer to use 1 x 8pin (& ATX) for the mobo and use 3 x 8pin for the card?

Thanks.
Click to expand...
8 pin eps can deliver up to 300w to the CPU which is more than enough for the 9800x3d .
 
PeterEv said:
Yes, I see a lot of negativity and suspicion about the 12VHPWR connector although most of that I think relates to high power cards that draw near to the max current/power rating of it, e.g. 5090s, etc.
Click to expand...
From the videos I've watched on the subject, that's true that the connector is most vulnerable with a high power draw card, but the low safety margin has the potential to be problematic even with a 9070 XT. I would not willingly use this connector. 3 independent cables is recommended, but I'd still take 1x independent and 2x connectors on the same cable, over a reverse 16 pin.
 
Tetras said:
From the videos I've watched on the subject, that's true that the connector is most vulnerable with a high power draw card, but the low safety margin has the potential to be problematic even with a 9070 XT. I would not willingly use this connector. 3 independent cables is recommended, but I'd still take 1x independent and 2x connectors on the same cable, over a reverse 16 pin.
Click to expand...
Thanks and I do share some of your concern..
So I'm thinking of using 3 x 8pin cables to the card and getting one of the following cables to feed the mobo given that will never demand over 300W so very safely within the 12VHPWR capacity..
I know that things go right until they don't but I was running a 4070 Ti Super using the 12VHPWR for months without issue so hopefully this is the safest best solution!

www.overclockers.co.uk

Seasonic PCIe 5.0 12VHPWR PSU Power Cable - Black

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PeterEv said:
Thanks and I do share some of your concern..
So I'm thinking of using 3 x 8pin cables to the card and getting one of the following cables to feed the mobo given that will never demand over 300W so very safely within the 12VHPWR capacity..
I know that things go right until they don't but I was running a 4070 Ti Super using the 12VHPWR for months without issue so hopefully this is the safest best solution!

www.overclockers.co.uk

Seasonic PCIe 5.0 12VHPWR PSU Power Cable - Black

Order Seasonic PCIe 5.0 12VHPWR PSU Power Cable - Black now online and benefit from fast delivery.
www.overclockers.co.uk www.overclockers.co.uk
Click to expand...
The EPS12v is a different connector to the PCIE 8 pin, so I don't think that would help you anyway. Honestly, I don't see the point in using it. I'd stick with the cable config you have, or just remove the 2nd EPS12v.
 
Tetras said:
The EPS12v is a different connector to the PCIE 8 pin, so I don't think that would help you anyway. Honestly, I don't see the point in using it. I'd stick with the cable config you have, or just remove the 2nd EPS12v.
Click to expand...
I hadn't realised that and should have checked, you've probably saved me a disaster, I'm very grateful to you..

I'll use a single EPS12v to the board and use 3 x 8pin to the gpu. :)

Thanks all..
 
PeterEv said:
So after an hour of BO6 running FRS4 Ultra settings 1440p 150+ fps, assuming HWMonitor is accurate, the 9070 XT TBP hit 411W. That's making me nervous supplying the card only with 1 x 8pin and 1 x 8pin with pigtail..

Given the 9800x3d is so frugal, do you think it might be safer to use 1 x 8pin (& ATX) for the mobo and use 3 x 8pin for the card?

Thanks.
Click to expand...

The pigtail is fine...
Each 8 pin can do 150w but PSUs will often output up to 300w from the 8pin socket because they issue cables with 2x 8pin connectors.

This is why Corsair and many others will do 2x 8pin to 12VHPWR. Their 8 pin spec can do 300w per cable. So using the daisy chain, or pigtail cable for one of the sockets is no problem at all
 
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