PCI-SIG Warns of Potential Overcurrent/Overpower Risk With 12VHPWR Connectors Using Non-ATX 3.0 PSU & Gen 5 Adapter Plugs

With next-gen approaching launch soon, one of the main components that users would want to update for their PCs is their PSU. This is due to new requirements and standards that have been set in place to deliver sustained and clean power, avoiding any issues in regard to transient spikes and power excursions. While there are many manufacturers who are bundling Gen 5 (12VHPWR) connectors with their existing PSUs, here’s why it’s a much better choice to invest in a real ATX 3.0 compliant PSU.

Here’s Why You Should Be Getting An ATX 3.0 Compliant PSU With Proper Gen 5 (12VHPWR) Connectors

PSU manufacturers are getting ready for a grand launch of their new ATX 3.0 designs but there are also certain manufacturers who are bundling their existing ATX 2.0 PSUs with Gen 5 connectors. As expected, upcoming graphics cards are going to be really power-hungry and would require up to 600 Watts of power.

What Is The 12VHPWR Connector?

The 12VHPWR Auxiliary Power connector is designed to deliver up to 600 watts directly to PCIe* Add-in Cards. This power connector is not compatible with the existing 2×3 or 2×4 auxiliary power connectors. The 12VHPWR connector power pins have a 3.0 mm spacing while the contacts in a 2×3 and 2×1 connector are on a larger 4.2 mm pitch. The 12VHPWR auxiliary power connector includes twelve large contacts to carry the power and four smaller contacts beneath carrying the sideband signals.

ATX 3.0 12VHPWR Connector Specs

The connector performance requirements are as follows:

  • Power Pin Current Rating: (Excluding sideband contacts) 9.2 A per pin/position with a limit of a 30 °C T-Rise above ambient temperature conditions at =12 VDC with all twelve contacts energized. The connector body must display a label or embossed H+ character to indicate support of 9.2 A/pin or greater. Refer to the approximate positioning of the marker on the 12VHPWR Right Angle (R/A) PCB Header.

ATX 3.0 Gen 5 vs ATX 2.0 Gen 5, What’s The Difference?

To hit their 600W power requirement, the graphics cards will be outfitted with either a single PCIe Gen 5 (12VHPWR) connector or three 8-pin connectors. If you are using an existing ATX 2.0 PSU, the only option you have is to either use a Gen 5 adapter or three 8-pin connectors to boot your card. In the case of an ATX 3.0 PSU with a Gen 5 plug coming from the main unit, you don’t have to worry about any adapters since that would be a direct connection from the PSU to the graphics card.

Now most manufacturers have told that using a standard 8-pin to 12VHPWR adapter should work just fine but according to PCI-SIG, that’s not the case. As you see, the 12VHPWR Gen 5 connector is designed to sustain a load of up to 600W while the 8-pin connector is designed to sustain a max load of 150W. And here’s where the safety risk arises.

Following is the mail forwarded PCI-SIG on the safety risks associated with using non-ATX 3.0 compliant Gen 5 PSUs:

Dear PCI-SIG Member,

Please be advised that PCI-SIG has become aware that some implementations of the 12VHPWR connectors and assemblies have demonstrated thermal variance, which could result in safety issues under certain conditions. Although PCI-SIG specifications provide necessary information for interoperability, they do not attempt to encompass all aspects of proper design, relying on numerous industry best-known methods and standard design practices. As the PCI-SIG workgroups include many knowledgeable experts in the field of connector and system design, they will be looking at the information available about this industry issue and assisting in any resolution to whatever extent is appropriate.

As more details emerge, PCI-SIG may provide further updates. In the meantime, we recommend members work closely with their connector vendors and exercise due diligence in using high-power connections, particularly where safety may exist.

Thank You,

The mail clearly states that there are safety risks associated with the PCIe Gen 5 connectors that have showcased thermal variance in PCI-SIG’s own testing. We wanted to get to the bottom of this issue and found out what’s causing this in the first place and which we did in the test results below.

Real-World Testing Shows Inaequately Balanced Load Using Gen 5 Power Adapters

So to see the thermal and more importantly, the power variance between a single Gen 5 connector and a 3x 8-pin to Gen 5 adapter, we used an existing Gen 5 PSU from a leading PSU manufacturer. A 600W load environment was set up and a Gen 5 adapter with the 12VHPWR connector at one end and two 8-pin connectors on the other was used. The 12VHPWR connector was plugged within the GPU while the two 8-pin connectors were plugged within the PSU.

Each of the two 8-pin connectors hit a maximum of 25A or around 300W of power which is twice its peak power rating of 150W. This is where PCI-SIG reports the thermal variance comes from but it’s not just the high-power running through the 8-pin connectors, there’s also an issue with the way the load is balanced through the adapter.

In the second test, we set up a 450W test load using an NVIDIA GeForce RTX 3090 Ti graphics card. Here, we used the reference adapter that comes with the card, a 12VHPWR to 3x 8-pin connectors. Here, instead of splitting the load equally through all three connectors, a single 8-pin connector is running 23.5A or 282W through it while the rest of the connectors are pulling 6-8A (80-100W). That means that there’s still a safety issue on a single 8-pin connector even if you are using three plugs.

Some adapter cables that use better materials such as alloy copper can allow more than 7A per pin so that’s 21A from three pins but even then, no one can guarantee stability and safety for long use cases, especially under 3x power excursions.

The Gen 5 connector can sustain up to 55 Amps so 600 Watts (50A) is within that limit and it the ATX 3.0 standard these are designed around can sustain 3x transient spikes. The breakdown of the two tests is as follows:

12VHPWR Connector To 2 x 8-Pin Adapter In 600W Test Load:

  • 1 x 8-Pin Connector = 25.4A or 304.8W (2x Increase Over 150W Rating)
  • 1 x 8-Pin Connector = 25.1A or 301.2W (2x Increase Over 150W Rating)

12VHPWR Connector To 3 x 8-Pin Adapter In 450W Test Load:

  • 1 x 8-Pin Connector = 25.34A or 282.4W (88% Increase Over 150W Rating)
  • 1 x 8-Pin Connector = 7.9A or 94.8W (Within 150W Power Rating)
  • 1 x 8-Pin Connector = 6.41 or 76.92W (Within 150W Power Rating)

Using the Gen 5 connector directly from an ATX 3.0 PSU results in no thermal or power variance since the cable is rated to sustain higher loads of up to 600W through a single cable. This may not be a cause of major concern now but considering the power spikes of 3x that we are expecting on the next-generation graphics cards (1800W ~ 600W x 3), this could kick the overcurrent and over-power feature of your PSU, resulting in power loss and PCs shutting down when hitting their power wall. As such, it is best to invest in a PSU that is Gen 5 and ATX 3.0 compliant to make sure your PC runs smoothly. We will be providing an update on this issue once we have more info from the PSU manufacturing community and PCI-SIG themselves.

Summary:

  • 12VHPWR connector is designed for 600W
  • The 8pin connector is designed for 150W.
  • Under 600W/450W load, more than 150W power is delivered through the 8pin
    the connector of a 16pin to 2x8pin splitter cable.
  • The current is not well balanced on the 16pin to 3x8pin splitter cable.
  • Native 12VHPWR connector for high power demanding usage such as graphics
    cards.

With that said, if you’re planning to build a new gaming PC with either an RTX 4090 or an RX 7900 XT, you better make sure to get a PSU within the respective wattage range on the ATX 3.0 standard. Currently, several PSU makers such as MSI, ASUS, Gigabyte, FSP Group Thermaltake, Seasonic, Silverstone & Cooler Master have announced their PCIe Gen 5 & ATX 3.0 compliant designs.

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