For example, the license model for both Windows Server and System Center changed from per-processor to per-core on general release of the 2016 versions in October, 2016. The means that if you renew Software Assurance (SA) on Windows Server or System Center licenses purchased when the per-processor licensing model was in effect, those licenses will transition to the per-core licensing model.

In that transition, Microsoft grants you by default a number of core licenses that is the product of the number of processors in your machine and a factor they specify. That factor is based on what Microsoft considers to be a typical number of cores in a machine running that software. If your machine has more cores than what Microsoft considers typical, and you accept the default core license grant, you can find yourself out of compliance and needing to buy more licenses.

But you can protect yourself from that possibility if you inventory your machines before renewing your SA. You must do the inventory before you renew your SA. You can self-inventory using the Microsoft Assessment and Planning Toolkit or other inventory tools and processes to achieve a time/date stamped inventory of hardware. If you do an inventory, Microsoft will grant you enough core licenses to fully license your machine when you renew your SA.

No matter whether you accept the default grant of core licenses or perform an inventory, the quantity of Software Assurance renewals needed is based on the core, not processor, count.

To reiterate, this situation can affect you when:

1. Microsoft changes the license terms and conditions of a license your department owns and
2. Your department owns current SA covering that license and
3. Your department renews that SA

If any of the above are not true, then your license terms and conditions remain the same as the day your department purchased the license(s). 

SA purchased through DoIT always ends on July 31st, and is prorated monthly to correspond with a term from two to three years long.