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PCI-SIG warns of potential overcurrent/overpower risk with 12VHPWR connectors using non-ATX 3.0 PSUs and Gen 5 adapter plugs

Here's Why You Should Be Getting An ATX 3.0 Compliant Power Supply With Proper Gen 5 (12VHPWR) Connectors 1
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With the upcoming release of the next generation, one of the main components that users would want to upgrade for their PCs is their power supply. This is due to the new requirements and standards that have been established to provide clean and sustained energy, avoiding any problems related to transient spikes and variations in energy. While there are plenty of manufacturers that are bundling Gen 5 (12VHPWR) connectors with their existing PSUs, here’s why it’s a much better option to invest in a real ATX 3.0 compatible PSU.

This is why you should get an ATX 3.0 compatible power supply with proper Gen 5 (12VHPWR) connectors

PSU manufacturers are preparing for a big launch of their new ATX 3.0 designs, but there are also certain manufacturers that are bundling their existing ATX 2.0 PSUs with Gen 5 connectors. As expected, the upcoming graphics cards will be very power hungry, requiring up to 600 watts of power.

What is the 12VHPWR connector?

The 12VHPWR auxiliary power connector is designed to provide up to 600 watts directly to PCIe* add-in cards. This power connector is not compatible with existing 2×3 or 2×4 auxiliary power connectors. The power pins on the 12VHPWR connector have a 3.0mm pitch, while the contacts on a 2×3 and 2×1 connector have a larger 4.2mm pitch. The 12VHPWR auxiliary power connector includes twelve large contacts to carry power and four smaller contacts below that carry sideband signals.

ATX 3.0 12VHPWR Connector Specifications

Connector performance requirements are as follows:

  • Power Pin Current Rating: (excluding sideband contacts) 9.2 A per pin/position with a 30°C limit T-Rise above ambient conditions to =12 VDC with all twelve contacts energized. The connector body shall display a raised H+ label or character to indicate support of 9.2 A/pin or higher. See the approximate position of the marker on the 12VHPWR right angle (R/A) PCB header.

ATX 3.0 Gen 5 vs ATX 2.0 Gen 5, what is the difference?

To reach its 600W power requirement, graphics cards will be equipped with either a single PCIe Gen 5 (12VHPWR) connector or three 8-pin connectors. If you’re using an existing ATX 2.0 PSU, the only option you have is to 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 connector coming from the main unit, you don’t have to worry about any adapters as that would be a direct connection from the PSU to the graphics card.

Now, most manufacturers have said that using a standard 8-pin to 12 VHPWR adapter should work fine, but according to PCI-SIG, that’s not the case. As you can see, the 12VHPWR Gen 5 connector is designed to support up to 600W load, while an 8-pin connector is designed to support 150W maximum load. And this is where the security risk comes in.

The following is the PCI-SIG mailed out on the security risks associated with using Gen 5 power supplies that are not ATX 3.0 compliant:

Dear PCI-SIG Member,

Please note that PCI-SIG has become aware that some implementations of the 12VHPWR connectors and assemblies have demonstrated thermal drift, which could lead to security concerns under certain conditions. While the PCI-SIG specifications provide the information necessary for interoperability, they do not attempt to cover all aspects of proper design, as they are based on many well-known industry standard design methods and practices. Since the PCI-SIG working groups include many experts in the field of system and connector design, they will review available information on this industry issue and assist in any resolution as appropriate.

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

Thank you

The email clearly states that there are security risks associated with PCIe Gen 5 connectors that have shown thermal variations in PCI-SIG’s own tests. We wanted to get to the bottom of this issue and find out what is causing it in the first place and what we did in the test results below.

Real world tests show unevenly balanced charging using Gen 5 power adapters

So, to see the thermal variance 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 charging environment was configured and a Gen 5 adapter was used with the 12VHPWR connector on one end and two 8-pin connectors on the other. The 12VHPWR connector connected to the GPU while the two 8-pin connectors connected to the power supply.

Each of the two 8-pin connectors maxes out at 25A or around 300W of power, which is double their maximum power rating of 150W. This is where PCI-SIG reports the thermal drift comes from, but it’s not just the high power going through the 8-pin connectors, there’s also an issue with how the load is balanced through the adapter.

In the second test, we configured a test load of 450 W with an NVIDIA GeForce RTX 3090 Ti graphics card. Here, we use the reference adapter that comes with the card, a 12VHPWR to 3x 8-pin connectors. Here, instead of dividing the load equally among 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 there’s still a security issue in a single 8-pin connector, even if you’re using three plugs.

Some adapter cables using better materials, such as copper alloy, can allow more than 7A per pin, which is equivalent to 21A of three pins, but even so, no one can guarantee the stability and safety under long-term use. , especially on 3x feed excursions.

A Gen 5 connector can support up to 55 amps, so 600 watts (50A) is well within that limit, and with the ATX 3.0 standard they are designed on, they can support 3x transient spikes. The breakdown of the two tests is as follows:

12VHPWR connector to 2 x 8 pin adapter at 600W test load:

  • 1 x 8-pin connector = 25.4 A or 304.8 W (2x increase over 150 W rating)
  • 1 x 8-pin connector = 25.1 A or 301.2 W (2x increase over 150 W rating)

12VHPWR connector to 3 x 8 pin adapter at 450W test load:

  • 1 x 8-pin connector = 25.34 A or 282.4 W (88% increase over 150 W rating)
  • 1 x 8-pin connector = 7.9 A or 94.8 W (within 150 W rated power)
  • 1 x 8-pin connector = 6.41 or 76.92 W (within 150 W rated power)

Using the Gen 5 connector directly from an ATX 3.0 power supply does not result in thermal or power variations as the cable is rated to handle higher loads up to 600W over a single cable. This may not be a big concern right now, but considering the 3x power spikes we’re expecting on next-gen graphics cards (1800W ~ 600W x 3), this could potentially remove the overcurrent and overcharge feature. from your power supply. resulting in a loss of power and PCs shutting down when they hit your power wall. As such, it’s best to invest in a PSU that supports Gen 5 and ATX 3.0 to ensure your PC runs smoothly. We will provide an update on this issue once we have more information from the PSU and PCI-SIG manufacturing community.

Summary:

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

That said, if you’re planning to build a new gaming PC with an RTX 4090 or RX 7900 XT, you’d better make sure you get a power supply within the respective wattage range in the ATX 3.0 standard. Currently, various manufacturers of power supplies such as M: YES, ASUS, gigabyte, FSP Group thermal, seasonal, silver stone & chiller master have announced their designs compatible with PCIe Gen 5 and ATX 3.0.

Products mentioned in this publication.

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