12VHPWR Connector/Cable: PSU’s Size (Watt) Does Matter!

Lots of talk (and drama) recently about the 12VHPWR connectors and cables, so I thought to write this article to clear out all this confusion. Although the 12 pin connector was released with the RTX 3000 series and there weren’t any major issues, it seems that the 12+4 connector (or 12VHPWR) raised lots of attention, and faced lots of critisism so far. But are things so serious, indeed?

Let’s make something clear from the start, addressing users unfamiliar with power supplies and their cables. The 12+4 pin connector, or 12VHPWR, has 12 pins, six for +12V (positive), six for COM (negative or common), and four for sense pins.

What do the Extra Four Sensor Pins do?

For starters, the four sensor pins don’t deliver current, but they are sense pins. Two of these sideband signals are required; the ones coming from the PCIe card are optional, while the ones coming from the power supply are required.

  • SENSE0 (Required)
  • SENSE1 (Required)
  • CARD_PWR_STABLE
  • CARD_CBL_PRES#

What is of interest to us are Sense 0 and 1 since these two pins are required and currently implemented on all 12VHPWR cables. These sense pins inform the graphics card of the PSU’s capability to deliver the power needed for the GPU. The following table shows the different configurations.

As you can see from the table above, to have the full power of 600W out of the 12VHPWR connector, both Sense 0/1 pins must be grounded. On the other hand, if these pins are both open, then the maximum sustainable power is only 150W, the same with the plain PCIe 6+2 connector. Naturally, if the graphics card doesn’t find these pins, it will assume they are both open, so 150W max.

600W Rated Cables vs 600W Set Cables

In the Seasonic TX-1600 PSU review that I wrote, I stated that according to Seasonic, this PSU is ATX v3.0 ready with up to 1000W loads, so it should have 450W 12VHPWR set connectors and not 600W. Beware, this doesn’t mean that its 12VHPWR cables cannot handle 600W, and they will melt with this amount of power! I suggested that according to Intel’s test plan, a 1000W PSU cannot have its 12VHPWR connector’s sense pins set for 600W but only 450W, especially since it has two!

Take a good look at the table below, and we will analyze this matter afterward. Note you won’t find this table anywhere else, so pay extra good attention to it!

 

This is what the Intel v3.0 Test Plan Calculator states. PSUs with 1100W or more can have 600W 12VHPWR connectors/cables, while PSUs within the 900-1099W range drop to 450W. The 300W and 150W settings are for lower-capacity units. This is to protect system restarts. Imagine a 750W PSU having a 12VHWR connector set for 600W output, in other words informing the graphics card that it can deliver up to 600W, powering an RTX 4090 with its power limit to the full (600W) and a power-hungry CPU. Most likely, you will face system restarts under heavy loads. This is why the PCI-Sig thought to implement the Sense 0/1 pins and provide protection against overloading the PSU. If your PSU has enough juice to provide, everything is fine, and you can go up to 600W. In the opposite case, it will be restricted according to its capacity.

The problems in 600/450/300/150 12VHPWR Connectors/Cables

Everything looks good in what the PCI-SIG thought about the different settings on the 12VHPWR cables and connectors, but so far, most brands ignore this guideline and provide 12VHPWR cables set for full power output (600). The problem in keeping a portfolio of different ratings of 12VHPWR cables and combining them with the corresponding PSUs led most brands to act like this: use the same 12VHPWR cables for all of their PSUs, regardless of capacity, and get over with the variations of the new connector. With the PCIe 6+2 cables, things were simple, you only had one connector type with no sense pins and settings, but the 12VHPWR is a different beast, making things more complex for all brands and manufacturers. A break-in period is required.

Imagine the two following scenarios:

Scenario #1: A user gets his new 1000W PSU which can power fine an RTX 4090, even with its power limit set at 600W, but its 12VHPWR connector’s Sense 0/1 pins are set for 450W. So the cable informs the graphics card that it cannot deliver more than 450W to it, which doesn’t stand, so the card is locked at 450W. This will create frustration for the user, who spent a notable amount to get a good 1000W PSU. From the moment, the RTX 4000 series doesn’t have the enormous power spikes that the PCIe 5 does.0 standard supports, there is no need for such tight power restrictions on the cables. This is what most brands thought, too.

Scenario #2: A user has a 750W PSU with a 12VHPWR connector set for 600W power output. The cable can handle full power, but the PSU will have a tough time under an extreme scenario, with an RTX 4090 at 600W and an Intel 13900K or an AMD Ryzen 9 7950x CPU running a heavy load at the same time. Most likely, the PSU will restart under a high load, especially if its over power protection is conservatively set, and this is the proper thing to do, to warn the user that he/she pushed it too far. Apart from a system restart, there won’t be any issues in the form of melt connectors, cables, etc., since the 12VHPWR connector can handle 600W. It is the PSU that will have a problem delivering them while also powering the CPU and the rest system parts.

I hope I made things clear with the two examples mentioned above.

What Is The Best To Do?

The solution is somewhere in the middle. A 1000W PSU can have a 12VHPWR connector set for 600W power output and work fine without any restart issues. Depending on the CPU’s power consumption, even a high-end 850W PSU could handle it. Most games don’t tax the CPU heavily. You can look at my article, NVIDIA RTX 4090 Detailed Power Analysis & Ideal Power Supply, to have a good idea of a system’s power consumption with an RTX 4090. There is no need for speculations, I have the Powenetics V2 system fully operational, and I can extract the power readings I want, including power spikes.

For 750W PSUs, I would suggest a 450W setting for the 12VHPWR connector to avoid pushing the PSU hard, and facing possible system restarts. Many PSUs have high over power protection triggering points; I have seen 750W PSUs delivering more than 1000W before shutting down, but overpowering your PSU is not the wisest thing to do.

In any case, you should remember this. The 12VHPWR connector’s Sense 0/1 pins setting doesn’t have to do with the power that it can handle! You can have a 600W-rated cable set at 450W because it is shipped with a 750W PSU. We might see lower power rating 12VHPWR cables, with fewer 12V and COM wires, anytime soon. This is a totally different case. But from the moment these cables will have their Sense 0/1 pins accordingly, they will be safe. If they don’t, then I will be here to highlight any possible problems!

 

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8 thoughts on “12VHPWR Connector/Cable: PSU’s Size (Watt) Does Matter!

  1. I noticed you removed as well the statement from the prior article saying that Seasonic said they will be updating the cables to 450W. Do you have any updated guidance from Seasonic on this; like if they will be sending out updated cables?

      1. I got a 1000 watt thermaltake gf3 and it came with a 450w cable. There was no mention of this anywhere online when I was reading about this PSU. Apparently I didn’t do enough research. Now my 4090 is going to be hamstrung. Can i just buy a 600 watt 12vhpwr cable and use that instead to get full power? If so I am actually having trouble finding actual 12vhpwr to 12vhpwr cables. They are all 12vhpwr to pci-e adapter cables. Frustrating.

        1. Same here with a GF3 850W. It came with a 300W cable. Can I connect a GF 4090 with it? That was the reason why I bought it.
          Now I am afaid to melt the cable and damage the card (once I get one).

          1. Even the GF3 750W comes with a 600W power rating cable! I asked TT and confirmed me that all of its PSUs use 600W 12VHPWR connectors. Now I don’t know if they will change this anytime soon, because the ATX v3.0 spec allows 600W connectors only on PSUs with >1100W capacity.

  2. So there can be different versions of the 12VHPWR cables sold by companies.
    This needs that the PSU companies (*and especially those cable-mod companies who sell cables indiviadually) should clearly advertise which 12VHPWR-cable is included in the box , since in theory (from what i saw in Aris schematics ) there could be 12VHPWR cables out in the market that can deliver only ….150watt ( when both sense pins 0&1 are open ).
    This can be disastrous for a user that will use such 12VHPWR cable with a high-power system , right ?

    –P.S. so the Palit RTX4090 you reviewed comes with a max 450watt version adapter or a max 600watt one ?
    Do we know which version of adapter comes with nVIDIA Founders models ? ( i assume 450watt max ? )
    Excellent analysis Aris , thanks !!

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