A multi-die package for a microprocessor provides a power management synchronization system. The package has a plurality of dies. Each die has a plurality of cores, including a single master core. A plurality of sideband non-system-bus inter-die communication wires communicatively couple the dies to each other for a purpose of synchronizing power management. The master core of each die is configured to use one and only one of the inter-die communication wires to transmit power management synchronization messages to each of the other master cores. The master core of each die is also configured to receive power management synchronization messages from each of the other master cores via one or more inter-die communication wires. The cores use this system of inter-die communication wires to synchronize management of resources that affect both the performance and power consumption of the cores.