PCI-SIG warns of potential overcurrent/overpower hazard with 12VHPWR connectors using non-ATX 3.0 PSU and Gen 5 adapters

With the imminent launch of the next generation, one of the main components that users would want to update for their PC is their power supply. This is due to new requirements and standards that have been put in place to provide sustained and clean power, avoiding any issues with transient spikes and power excursions. Although many manufacturers bundle Gen 5 (12VHPWR) connectors with their existing PSUs, here’s why investing in a genuine ATX 3.0 compatible PSU is a much better choice.

Here’s why you should get an ATX 3.0 compatible PSU with proper Gen 5 (12VHPWR) connectors

PSU manufacturers are gearing up for a big launch of their new ATX 3.0 designs, but some manufacturers are also bundling their existing ATX 2.0 PSUs with Gen 5 connectors. As expected, upcoming graphics cards will be very power hungry in energy and will require up to 600 watts of power.

What is the 12VHPWR connector?

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

ATX 3.0 12VHPWR Connector Specifications

The connector performance requirements are as follows:

• Power pin current rating: (excluding sideband contacts) 9.2 A per pin/position with 30°C T-Rise limit above ambient temperature conditions at = 12 VDC with all twelve contacts energized. The connector body shall display an embossed H+ character or label to indicate support for 9.2 A/pin or greater. Refer to the approximate placement of the marker on the right angle (R/A) 12VHPWR PCB header.

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

To achieve their required power of 600 W, the graphics cards will be equipped with a single PCIe Gen 5 (12VHPWR) connector or three 8-pin connectors. If you’re using an existing ATX 2.0 power supply, the only option you have is to use a Gen 5 adapter or three 8-pin connectors to boot your board. 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 adapters as it would be a direct connection from the PSU to the graphics card.

Now most manufacturers said that using a standard 8 pin to 12VHPWR adapter should work just fine, but according to PCI-SIG it doesn’t. As you see, the 12VHPWR Gen 5 connector is designed to support up to 600W load while an 8-pin connector is designed to support a maximum load of 150W. And this is where the security risk arises.

Here is the mail from PCI-SIG about the security risks associated with using non-ATX 3.0 compliant Gen 5 power supplies:

Dear PCI-SIG member,

Please note that PCI-SIG has become aware that some implementations of 12VHPWR connectors and assemblies have demonstrated thermal variation, which could lead to safety issues under certain conditions. Although the PCI-GIS specifications provide the information needed for interoperability, they do not attempt to encompass all aspects of proper design, relying on many of the industry’s best-known standard design methods and practices. industry. As the PCI-SIG working groups include many knowledgeable experts in the field of connector and system 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 recommend members work closely with their connector suppliers and exercise due diligence when using high power connections, especially where safety issues may exist.

Thanks,

The mail makes it clear that there are security risks associated with PCIe Gen 5 connectors that exhibited thermal variance in PCI-SIG’s own testing. We wanted to get to the bottom of this issue and find out what was causing it in the first place and what we did in the test results below.

Real-world testing shows poorly balanced charging using Gen 5 power adapters

So to see the thermal and more importantly the power variation between a single Gen 5 connector and a 3x 8 pin to Gen 5 adapter, we used an existing Gen 5 PSU from a major PSU manufacturer power supply. A 600W charging environment was configured and a Gen 5 adapter with the 12VHPWR connector on one end and two 8-pin connectors on the other was used. The 12VHPWR connector was plugged into the GPU while the two 8-pin connectors were plugged into the PSU.

Each of the two 8-pin connectors maxes out at 25A or about 300W of power, which is twice its peak power rating of 150W. That’s where PCI-SIG reports the thermal variance is coming 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 across the adapter.

In the second test, we configured a 450W test load using an NVIDIA GeForce RTX 3090 Ti graphics card. Here we used the reference adapter that came with the board, a 12VHPWR to 3x 8 pin connector. Here, instead of spreading the load equally across all three connectors, a single 8-pin connector passes 23.5A or 282W while the rest of the connectors draw 6-8A (80-100W). This means there is still a safety issue on a single 8 pin connector even if you are using three sockets.

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

A Gen 5 connector can handle up to 55 amps, so 600 watts (50 A) is within that limit and the ATX 3.0 standard they are designed around can handle 3 transient peaks. 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 = 25.4 A or 304.8 W (2x increase from 150 W)
• 1 x 8-pin connector = 25.1 A or 301.2 W (2x increase from 150 W)

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

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

Using the Gen 5 connector directly from an ATX 3.0 PSU results in no thermal or power variation since the cable is designed to support higher loads of up to 600W through a single cable. This may not be a major cause for concern at the moment, but given the 3x power spikes we expect on next-gen graphics cards (1800W~600W x 3), this could trigger the feature overcurrent and overcharging of your PSU, causing PCs to lose power and shut down when they hit their power wall. As such, it’s best to invest in a Gen 5 and ATX 3.0 compatible PSU to ensure your PC runs smoothly. We will provide an update on this issue once we have more information from the PSU manufacturer community and PCI-SIG themselves.

Summary:

• 12VHPWR connector is rated for 600W
• The 8-pin connector is designed for 150W.
• Under a 600W/450W load, over 150W of power is delivered through the 8-pin
  the connector of a 16-pin to 2×8-pin splitter cable.
• Current is not well balanced on the 16-pin to 3×8-pin splitter cable.
• Native 12VHPWR connector for power demanding use such as graphics
  maps.

That said, if you’re planning on building a new gaming PC with an RTX 4090 or RX 7900 XT, you better make sure you get a PSU in the respective power range on the ATX 3.0 standard. Currently, several PSU manufacturers such as MSI, ASUS, Gigabyte, FSP Group Thermaltake, Seasonic, Silverstone, and Cooler Master have announced their PCIe Gen 5 and ATX 3.0 compliant designs.