A new Intel ATX12V spec, version 3.0, brings some significant changes. After many years, we finally have a new 12+4 pin connector, also named 12VHPWR. This connector and its power rating bring some major changes to PSUs from now on. First of all, it is mandatory for all PSUs with more than 450W power ratings, so most PSUs will have one.
Thanks to the 600W maximum that the 12VHPWR can deliver, in reality, it is even more, there have to be some changes in the majority of existing PSU platforms allowing for increased tolerance to power spikes.
The Nvidia RTX 3000 series has several compatibility issues even with powerful PSUs because of the increased power spikes. It seems the new generation of GPUs will be even worse, so Intel took the PCIe CEM (Card Electromechanical specification) in mind and came up with some new requirements, which will ask for some modification in older platforms primarily to meet them.
The most important change is that PSUs with over 450W capacity, which should have a 12VHPWR installed, have to be able to withstand various power spikes levels with the highest being 200% of their max-rated capacity for a period of 100μs and a 10% testing duty cycle. There are three more levels, at 180/160/120% with the power spike period increasing to 1/10/100ms and the testing duty cycle also increasing to 20/25/50%.
There is a change in the load regulation at +12V allowing for -8% on the PCIe connectors, to cope with the increased transient load levels and -7% for the other connectors. Moreover, this is the first time that the ATX spec allows for a higher than 12V nominal voltage, at up to 12.2V.
Another significant change affecting all manufacturers is that they have to include in the PSU's power spec label extra information regarding the T1 and T3 timings and also label the 12VHPWR connectors, according to the max power that they can deliver.
Finally, from now on, the GPU power limits will be adjusted accordingly based on the power supply's capabilities to avoid compatibility issues. There can be issues for multi-GPU systems if the optional CARD_CBL_PRES# signal is not present, to inform the PSU to adjust the sense wires on its 12VHPWR connectors accordingly. In any case, you will need 1800-2000W PSUs to exploit 600W graphics cards fully.
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Disclaimer: Aris Mpitziopoulos is Tom's Hardware's PSU reviewer. He is also the Chief Testing Engineer of Cybenetics and developed the Cybenetics certification methodologies apart from his role on Tom's Hardware. Neither Tom's Hardware nor its parent company, Future PLC, are financially involved with Cybenetics. Aris does not perform the actual certifications for Cybenetics.