ATX Version 3.0 Multi Rail Desktop Platform Power Supply

Design Guide

ID 336521
Date 01/02/2022
Version 2.0
Document Table of Contents

Processor Configurations - RECOMMENDED

The processor power in a desktop computer is provided by the 12V2 power rail of power supplies with multiple power rails. To meet the desktop processor power needs a desktop power supply must provide the current value list in Table 2-1 for the 12V2 voltage rail. Table 2-1 shows the various processor current requirements represented by the desktop processor’s TDP. If a power supply only has one 12V rail then Table 2-1 shows the amount of current that needs to be dedicated to the desktop processor in a system level power budget.

Table 2-1: 12V2 Current for Processor Configurations

PSU 12V2

Capability Recommendations

Processor TDP

Continuous Current

Peak Current

165 W

37.5 A

40 A

125 W

26 A

39 A

65 W

23 A

34 A

35 W

11 A

19 A

  1. If the power supply supports, the 240 VA Energy Hazard protection requirement then current levels for the 12 Volt rail above 18 Amps must be split into multiple 12 V rails.
  2. Continuous current is defined for the processors PL2 (Turbo) power limit since desktop processors are expected to stay at PL2 for many seconds, sometimes close to 1 minute. For a PSU any time over 1 second is considered Continuous current.
  3. Peak Current is defined for the processor’s PL4 which defines Peak current for a max time of 10 ms.

All future processor power/PSU current requirements will be defined in a document titled ATX12VO and ATX12V PSU Design Guide Addendum (# 621484) that is applicable to both Single Rail and Multi Rail ATX Power Supplies. Refer to that document for details of where these values come from.