PCI-SIG warns of potential overcurrent/overcurrent hazards with 12VHPWR connectors using Non-ATX 3.0 PSU & Gen 5 adapter sockets

With the launch of the next generation soon approaching, one of the main components that users may want to update for their PC is the PSU. This is due to the new requirements and standards that have been put in place to provide sustainable and clean energy, avoiding any issues regarding transit altitudes and power flights. While there are many manufacturers that bundle Gen 5 (12VHPWR) connectors with existing PSUs, here’s why it’s a much better option to invest in a true ATX 3.0 compatible PSU.

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

PSU manufacturers are preparing for a major product launch New ATX 3.0 designs but there are also some manufacturers that are bundling existing ATX 2.0 PSUs with Gen 5 connectors. As expected, upcoming graphics cards will be really power-hungry and will require up to 600 watts of power.

What is a 12VHPWR connector?

The 12VHPWR auxiliary power connector is designed to deliver up to 600W directly to additional PCIe* cards. This power connector is not compatible with existing 2×3 or 2×4 auxiliary power connectors. The 12VHPWR connector’s power pins have a spacing of 3.0mm while the contacts on the 2×3 and 2×1 connectors are 4.2mm larger. The 12VHPWR auxiliary power connector includes twelve large contacts for the power carry and four smaller contacts below the sideband signal carry.

ATX 3.0 12VHPWR Connector Specifications

Conductor performance requirements are as follows:

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

ATX 3.0 Gen 5 vs ATX 2.0 Gen 5, what’s the difference?

To achieve the 600W power requirement, graphics cards will be equipped with either one PCIe Gen 5 header (12VHPWR) or three 8-pin headers. If you’re 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 the Gen 5 plug 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 I tell most manufacturers that using a standard 8-pin to 12VHPWR converter should work fine but according to PCI-SIG, this is not the case. As you can see, the 12VHPWR Gen 5 connector is designed to handle a load of up to 600 watts while the 8-pin connector is designed to handle a maximum load of 150 watts. This is where the safety risks come in.

The following is a PCI-SIG message forwarded via mail regarding the safety risks associated with the use of 5th generation PSUs not compatible with ATX 3.0:

Dear PCI-SIG member,

Please be aware that PCI-SIG has recognized that some applications of 12VHPWR connectors and assemblies have exhibited thermal variance, which can lead to safety issues under certain conditions. Although the PCI-SIG specification provides the information necessary for interoperability, it does not attempt to include all aspects of appropriate design, relying on many known industry methods and standard design practices. Since the PCI-SIG working groups include many experts who are knowledgeable in the field of connector and system design, they will consider the available information on this industry problem and assist with any solution to whatever extent is appropriate.

As more details emerge, PCI-SIG may provide more updates. In the meantime, we recommend that members work closely with connector suppliers and exercise due diligence in the use of high-power connections, particularly when there are safety concerns.

Thank you,

The mail clearly states that there are safety risks associated with PCIe Gen 5 connectors that showed thermal variance in a private PCI-SIG test. We wanted to get to the heart of this issue and find out what caused it in the first place and what we did in the test results below.

Real world testing shows insufficiently balanced load with 5G power inverters

So to figure out the heat 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 is set up and a Gen 5 adapter is used with a 12VHPWR connector on one end and two 8-pin connectors on the other. The 12VHPWR connector is connected to the GPU while two 8-pin connectors are connected inside the PSU.

The two 8-pin connectors each delivered a maximum of 25 amps or about 300 watts of power which is twice the peak power rating of 150 watts. This is where the PCI-SIG notes that thermal variance comes from but not only the high power running across the 8-pin connectors, there is also an issue with the way the load is balanced through the transformer.

In the second test, we set up a 450W test load with an NVIDIA GeForce RTX 3090 Ti graphics card. Here, we used the reference adapter that came with the card, and the 12VHPWR to 3x 8-pin connectors. Here, instead of dividing the load evenly across all three conductors, one 8-pin conductor runs 23.5 amps or 282 watts through it while the rest of the conductors draw 6-8 amps (80-100 watts). This means that there is still a safety issue with a single 8-pin connector even if you use three sockets.

Some transformer cables that use better materials like copper alloy can allow more than 7 amps per pin, 21 amps from three pins, but even then, no one can guarantee stability and safety for long use cases, especially under 3x power trips .

A Gen 5 connector can handle up to 55 amps, so 600 watts (50 amps) falls within that, and the ATX 3.0 standard built around it can maintain 3x transient spikes. The details of the two tests are as follows:

12VHPWR Connector to 2 x 8-Pin Adapter at 600W Load Test:

• 1 x 8-Pin Connector = 25.4A or 304.8W (2x increment over 150W rated)
• 1 x 8-Pin Connector = 25.1A or 301.2W (2 times increment x over 150W)

12VHPWR Connector to 3 x 8-Pin Adapter at 450W Load Test:

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

Using a Gen 5 connector directly from an ATX 3.0 PSU results in no thermal or power difference since the cable is rated to handle higher loads of up to 600 watts through a single cable. This might not be a cause for major concern now, but given the 3 times the power spikes we’d expect on next-gen graphics cards (1800W ~ 600W x 3), this could lead to overcurrent and overpowering the advantage of your PSU, This results in a loss of power and computers shutting down when they hit a power wall. As such, it’s best to invest in a PSU that’s compatible with Gen 5 and ATX 3.0 to make sure your PC runs smoothly. We will provide an update on this issue as soon as we have more information from the manufacturing community at PSU and PCI-SIG themselves.

Summary:

• 12VHPWR connector is designed for 600W
• The 8pin connector is designed for 150 watts.
• Under 600W/450W load, more than 150W is delivered through 8pin
  16pin to 2x8pin splitter cable connector.
• The current is not well balanced on the 16pin to 3x8pin splitter cable.
• Original 12VHPWR connector for high power demand like graphics
  cards.

With that said, if you’re planning to build a new gaming PC with either an RTX 4090 or RX 7900 XT, you’d better make sure you get a PSU within the respective wattage range on the ATX 3.0 standard. Currently, many PSU makers like MSIAnd the ASUSAnd the GBAnd the FSP . group ThermaltakeAnd the seasonalAnd the Silverstone & More cool head They announced their PCIe Gen 5 and ATX 3.0 compatible designs.