PCIe* Add-in-Card and PSU Power Budgets

Three dominant power demands dictate the total system power provisioning:

1. CPU power consumption
   1. PCIe* Add-in Card power level

1. Rest-of-Platform power demand

Rest-of-Platform(ROP) collectively includes anything in a system (memory, storage, motherboard, peripherals, etc.) not including the PCIe* Add-in Cards or CPU. Table 3-2 provides examples that generally balance these three power demands to obtain an overall PSU power rating. The PCIe* power entries in the table are standard power levels for PCIe Add-in Cards defined in the PCIe* CEM 5.0 Specification. As a consequence of the introduction of 450 W and 600 W Card power levels, the wide range of possible PCIe* card power demands plays a dominant role in setting total platform power supply ratings.

These configurations will also serve as test cases for evaluating power supply excursions. The peak power demands of the PCIe* Add-in Cards at each power level can guide the peak power demands of the PSU.

In cases where a PCIe* Add-in Card has a sustained power not listed, use these values as a minimum value for all cards up to these power levels. The table below is seen as a minimum power level based on Rest of Platform (ROP) power. The ROP assumptions are shown in Table 3-2 below. If a system designer plans more ROP power, the overall platform power budget for a system must be increased. If a system designer plans less ROP power, then the PSU size can also decrease. In the case of ROP values lower than what is shown in Table 3-2, the calculations should be done for Peak Power Requirement for this specific system. If the Peak Power requirements for this specific system exceed the values shown in Table 3-2 than a PSU with support for higher peak power levels would be needed.

The CPU continuous power comes from Table 2-1, taking the current value and multiplying by 11.2 Volts to create a power value and round up slightly. The CPUs used in these examples are the 65w TDP for the first row and 125w TDP for all other rows.

This is a recommendation for a Power Budget and guidance that is needed to define PSU Peak Power Excursion levels. These power budgets also assume only one PCIe* Add-in Card will use these power excursions. If more than one PCIe* Add-in Card is installed in the system, then the system designer needs to verify the power supply can provide enough power for all components in the system including the Peak Power Excursions of all components. This industry standard PSU Design Guide does not provide a standard definition for that type of system design.

Table 3-2: PCIe* AIC and PSU Power Budget used for Peak Power Excursion Test Cases

1. 1. If Rest of Platform power is higher than what is in the table, increase the PSU size respectively.
   2. If Rest of Platform power is lower than what is listed in the table the PSU size can also be reduced, but Peak Power requirements are also expected to increase beyond what is listed in Table 3-3.