ATX Version 3.0 Multi Rail Desktop Platform Power Supply

Design Guide

ID 336521
Date 02/01/2023

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Document Table of Contents

PCI Express* Add-in Card Considerations

The PCI Express* (PCIe*) Card Electromechanical Specification (CEM Spec) provides thermal, power, mechanical, and signal integrity design guidance for the PCI Express* Add-in Card (AIC) form factor. This includes the card’s electrical and mechanical interface with a host system board, chassis, and power supply.

The 5.0 Revision of the PCIe* spec introduces four significant updates that directly affect this power supply specification:

  1. A Power Excursion allowance was introduced to support brief, high current demands on power, beyond the rated TDP.
  2. The maximum power consumption for a single Add-in Card was doubled to 600 W. This is the per-card limit from all sources combined.
  3. A new 48V (nominal) power rail was added.
  4. Two new Auxiliary Power Connectors were introduced to provide the full 600 W on a single cable connector. The new 12VHPWR connector supports 600W on the 12V rail while the 48VHPWR provides 600W on the 48V rail. Four new sideband signal conductors permit simple signaling between the Add-in Card and power supply.