Demystified: This is how NVIDIA's 4-way adapter for the 12VHPWR port of the GeForce RTX 4090 really works!

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Who doesn’t know it, the funny adapter from NVIDIA, with which you can merge four PCIe 6+2 pin cables to be able to run graphics cards with up to 600 watts? If you only connect three plugs, you’ll only get 450 watts and with two plugs, the PC won’t start at all with a bit (read full article...)
 
Just wanted give a feedback on your excellent post about the 12VHPWR connector pinout. There's actually no problem with the Alibaba/Aliexpress or any other Chinese cables, provided you triple check the pinout and the cable construction before plugging it to your expensive hardware.

I just bought from Aliexpress a cable for my RTX 4080 FE. It's a 12VHPWR connector on one end and two 8-pins connectors on the other end, each connector with 6 pins connected (3 positives and 3 negatives), and 2 free pins.

The sense pins are just jumped from negative wires.

I'm using this cable for a week now, and it's working great. No issues so far.

It should work fine for the 600W rated power limit. 600W divided by the 6 pairs of wires on the connector means 100W per pair, which is 8,3 Amps per pair of wires. The cable is made of AWG 18 wires, which is rated for 14 Amps... So the cable will handle the current just fine.
 

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This configuration (just use 2pin sense) not work in my RTX4090 Galax, just the original converter of Galax. The computer simply dont boot up.
 
Hi there, I'm building my own 12VHPWR adapter at present and am banging my head against the sense signal diagram here as it appears to conflict with Intel's ATX 3.0 spec - long story short, I believe the pins Sense 0 and Sense 1 are confused in Igor's diagram (NB that this is irrespective of the issue of "mirroring" the plug - I'm talking about the two left pins being confused here).

Looking at Intel's ATX 3.0 spec, diagram page 55 and pin-out table on p 57, the leftmost pin should be S4, translating to Sense 1, and the next one (centre-left) S3, translating to Sense 0 - as opposed to Igor's diagram reading Sense 0 - Sense 1, left-to-right.
The encoding in Intel's table (page 28) is identical to Igor's: Sense 0 distinguishes between 450/600W, Sense 1 needs to be on GND to get to 450W and beyond.

It does not make a difference if you want to get to 600W as both pins need to be pulled to GND, for 450W (as in my case) it does, though.

Can anyone confirm? Thanks!
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It doesn't make a difference for RTX 4090. Both left pins connected to ground for 600W, that's the standard for all proprietary 12VHPWR cables for ATX PSUs before ATX 3.0. Here my seasonic cable, both sense pins connected to ground at one 8-Pin PSU-connector.

1690114083598.png

The real ATX 3.0/PCIe 5 functions on the 12VHPWR connector are these, it naturally doesn't work with an ATX 2.0 PSU and today there is no PCIe 5.0 graphic card.


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It doesn't make a difference for RTX 4090. Both left pins connected to ground for 600W, that's the standard for all proprietary 12VHPWR cables for ATX PSUs before ATX 3.0. Here my seasonic cable, both sense pins connected to ground at one 8-Pin PSU-connector.

Anhang anzeigen 26756

The real ATX 3.0/PCIe 5 functions on the 12VHPWR connector are these, it naturally doesn't work with an ATX 2.0 PSU and today there is no PCIe 5.0 graphic card.


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Cheers, and thanks for the swift feedback! You diagram appears to confirm my reading of the Intel spec, suggesting that Igor’s drawing has two pins confused. To you point on ATX 3.0 proliferation: In the meanwhile, I took an aftermarket 12VHPWR L-adapter apart and can confirm that both relevant sense pins are pulled ro GND in the adapter already, so whatever the sense wires of connected cables do from there onwards appears to be irrelevant- looks like that apart from in NVidias own 4-to-1 cable, no one seems to make much use of the sense feature and just assumes a full 600W of power available at the PSU…
 
Yes, most RTX 4090 cards have (thankfully) 450W maximum power draw, as my Inno3D.
 
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