General
Understanding ATX 3.0, PCI-E 5.0 and ATX3.1 terminologies for PC Power Supply
Previously on ATX 2.x Standards
The ATX12V 2.x standards incrementally made morphing of PSUs from AGP era into PCI-E era where the major heavy lifting of power load is now done by 12V rail(s). While the AGP slot could only draw 1A on the 12V and upto 6A on 3.3V rail. The CPU power draw was also shifted to 12V rail instead of the 5V rail previously on Pentium series of CPUs hence we saw humongous amount of amperage on 5V and 3.3V rails for this specific reason. The ATX motherboard connector was extended into 24-pin and 12V-CPU 4+4 pin was implemented. The 12V lines were further improved to provide 20A on each rail. The minimum allowed efficiency bar was raised to 70% while recommended effeciency baseline was set at 80%. Furthermore the Energy Star compliances were made available in two revisions. While the regulation and ripple characteristics were carried forward from ATX 1.x standards, the most notable change was complete shift of power from 5V and 3.3V rails to the 12V rail(s).
PCI-E 5.0 Standard
As there were no considerations for high-power transient loads / spikes in PCI-E 4.0 standard, the PCI-E 50 standard rises limit of PCI-E proprietary power to 600W from 450W (of PCI-E 4.0) and ensures limits on short-term load peaks of 3 times the average power consumption in an interval of upto 100 microseconds. For example if we use a 600W GPU, the allowed maximum spike load will be limited to 1800W. Not only short term but relatively longer term load for 10milliseconds was defined by PCI-E 5.0 standard to be twice the averae power. It is also important to note that the factory overclocked or enthusiast variants of the high-end GPUs may not adhere to this maximum spike load limitation.
ATX 3.0 Standard
Moving past the ATX 2.x, into the ATX 3.0 standard power supplies qualifying for ATX 3.0 standard also adhere to PCI-E 5.0 standard by introducing 12VHPWR connector with auxiliary 4 sense pins as well. The ATX 3.0 standard enforces the transient load spike implementations from PCI-E 5.0 standard. For the first time ATX 3.0 defines target values above the nominal power of the power supply. These state that the PCIe connections for the graphics cards must allow load changes of up to three times the power consumption. For example, if we look at a 1200-watt power supply with a graphics card of the 600-watt class, 300 watts are budgeted for the CPU and another 300 watts are assigned to all other components. The power supply in this example must be able to achieve a power of (3*600W)+300W+300W, i.e. a total of 2400 watts, over a very
small time period. This is where ATX 3.0 and ATX 2.X power supplies differ the most.
The 12VHPWR Connector
The last time new connectors were introduced was in 2013 for PCIe revision 2. The 8-pin PCIe power connector could provide up to 150 watts whereas the familiar 6-pin one was only specified for 75 watts. More demanding graphics cards would need up to three of these power connectors. The new 12VHPWR connector is much more compact and able to supply up to 600 watts of power via a single connector. It has 12 cores for the electricity supply (6x12V and 6x ground) and four signal lines that serve as communication interface between power supply and add-in cards.
The new sense lines of the 12VHPWR connector improve the interaction between power supply and PC. An ATX 2.X power supply does not know whether and how many consumers are connected. Graphics cards also are not provided with any information from the power supply. The new 12VHPWR connectors have the ability to work smarter. Using the sense pins, the power supply can communicate its maximum power via SENSE0 and SENSE1. The maximum load of a 12VHPWR can be defined in four steps from 150, 300 and 450 to 600 watts.
On the other hand, PCIe 5 explicitly states that the continuous power consumption of 600 watts must not be exceeded by the connected card. Depending on how the PSU sets the maximum allowed load, the graphics card will not attempt to exceed it, but may run with reduced performance or not work properly, if the PSU power is rated lower than the GPU requirement. Certain features of the 12VHPWR connector are optional and ensure compatibility with previous standards. The existence of a 12VHPWR connector on a graphics card does not give an indication about its performance or power consumption.
The connector compliance for 12VHPWR
It is possible to use an adapter cable from the previous PCIe connector to the new 12VHPWR connector with an ATX 2.X power supply. However, Intel recommends that the new connector socket or fixed 12VHPWR cables are only attached to power supplies that fully comply with ATX 3.0. This is emphasized by the fact that the latest PCI Express revisions only describe the high power peaks in combination with the 12VHPWR cable. It is becoming apparent that the market is looking for loopholes to introduce users to this new technology as quickly and for the lowest cost possible. Special attention is required whether a manufacturer clearly labels a power supply as ATX 3.0 compliant, to ensure that all necessary standards for future graphics cards are met. be quiet! is overhauling its portfolio and launches future-proof power supply units.
From ATX 3.0 to 3.1
Key Differences
- Real Differences Between ATX 3.0 and ATX 3.1
The changes between ATX 3.0 and ATX 3.1 go far beyond just the cable. They include electrical requirement updates and connector design improvements — even on the PSU’s modular panel side.
1. Hold-up Time Requirement
* ATX 3.0: Minimum of 17 ms hold-up time at 100 % load — the PSU must keep output voltages stable for that time after input power is lost.
* ATX 3.1: Reduced to 12 ms at 100 % load, but still recommends 17 ms at 80 % load for stability.
This reduction allows smaller capacitors inside the PSU, improving efficiency and reducing cost. - High-Power Connector
* ATX 3.0: Uses the original 12VHPWR connector.
* ATX 3.1: Uses the new 12V-2×6 connector with:
12V and GND pins extended by +0.25 mm for better contact and lower thermal resistance.
Sense pins shortened by –1.5 mm, so they make contact last, avoiding incorrect readings or arcing when partially inserted.
These changes apply to both the cable and the male connector on the PSU’s modular panel.
• Some manufacturers kept the same cable since it meets the load capacity, and only changed the male connector on the modular panel with the new pin dimensions as shown in the images (courtesy igorslab):
Which one to choose?
- ATX 3.1 is generally recommended for new builds or upgrades, especially if you’re using a high-end GPU or plan to upgrade to future hardware.
- ATX 3.0 is acceptable if you already have a high-quality ATX 3.0 PSU: and it meets the power requirements of your system.
