SENSE0 & SENSE1 (Required)

Support for the SENSE0 & SENSE1 sideband signals is required for both power supplies and Add-in Cards mounting the 12V-2x6 connector. SENSE0 & SENSE1 communicate important 12V power level information from the PSU to the Add-in Card, and must be configured by the power supply. These sideband signals set the maximum power available to the Add-in Card the though the cable during both initial power up and during normal system operation.

Four power levels, 600, 450, 300, and 150 watts, are configured by the SENSE0 and SENSE1 signals to allow power supplies having different power capacities (and Add-in Cards with a range of power demands) to deliver 12V power using a common connector interface. The SENSE0/SENSE1 encodings that define the power levels are detailed in Table 3-6.

The PCIe CEM 5.1 specification designates these levels as “Connector Initial Permitted Power” and “Connector Maximum Permitted Power” to indicate the power limits supported by the power supply through the 12V-2x6 Auxiliary Power Connector. The maximum power levels indicated are the maximum sustained power supported by this Auxiliary Power Connector alone, and do not include power drawn separately through the motherboard card edge connector, separate power cable plugs, or any other source.

A power supply supporting the 12V-2x6 auxiliary power connector must short the appropriate SENSE signals to ground or leave them floating at a high impedance (Open) to indicate the 600 watt, 450 watt, and 300 watt sustained power limits of the power supply. For a non-modular power supply with a hard-wired 12V-2x6 cable plug assembly, the SENSE0 and SENSE1 pins may be configured with a jumper wire to ground, at the cable plug end, within the body of the plug itself, or internal to the power supply.

Support for the 150 watt sustained power level is configured by providing a short between the SENSE0 & SENSE1 signals, presenting a 0 ohm resistance between the SENSE0 and SENSE1 pins at the cable plug. For a non-modular power supply with a hard-wired 12V-2x6 cable plug assembly, the SENSE0 and SENSE1 pins may be united with a jumper wire at the cable plug end, within the body of the plug itself, or internal to the power supply.

For the 150 watt configuration, the SENSE0 & SENSE1 pins must be shorted to each other but must remain floating (high impedance) with respect to ground. If these pins were also (mistakenly) shorted to ground, the card would misread the available power as 600 watts instead of 150 watts.

A modular power supply supporting detachable 12V-2x6 cables, must configure the SENSE0 and SENSE1 pins only within the power supply, for all power levels, to ensure correct operation when interchangeable “double-ended” 12V-2x6 cable assemblies are used.

These SENSE signals must not change state while PCI Express CEM Add-in Card edge has the main +3.3V applied. Support for the SENSE0/SENSE1 sideband signals is independent of the two optional sideband signals defined for the 12V-2x6 connector (CARD_​PWR_​STABLE & CARD_​CBL_​PRES#).

Table 3-6: PCI Express* 12V-2x6 Connector Power Limits

1. For an Add-in Card to draw any power through the 12V-2x6 Connector, it must monitor SENSE0 and SENSE1.
2. 150 W is indicated by SENSE0 and SENSE1 being connected by a resistance of 0 Ω.
3. An Add-in Card may draw up to the maximum permitted power defined in this table in addition to other power sources.