What is Dynamic Link Width Modulation?
With the large amount of I/O capabilities of the EPYC processor, it is important that the EPYC processor be able to manage the power consumption allocated and used by the I/O subsystems. The management of this power ensures that the maximum performance can be achieved. The Power Management Unit (PMU) manages the control of the I/O subsystems and more specifically the Infinity Fabric interface that is utilized in a two-socket EPYC based platform. By being able to monitor and adjust the Infinity Fabric's data path width, the PMU can save power from the I/O subsystems and divert that power towards the cores to increase performance.
As an example, if the workload being generated between the processors on the Infinity Fabric is low, the Power Management Unit (PMU) can downsize the data path from an x16 link all the way down to an x2 data width link. The power being saved by disabling those I/O signals can be utilized by the CPU cores allowing them to increase their speeds. If the I/O requirements of the Infinity Fabric increases, the datapath width can be increased again back up to x16. The control of these links is dynamic and does not require any input or setup as it is built into the AMD EPYC SoC.
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