When you deploy Windows Server 2012 R2 through Windows Deployment Services (WDS) Pre-Boot Execution Environment (PXE), the server CPU usage spikes to 100%. In this situation, client computers may freeze while waiting for a response from the PXE server.
This issue occurs because of a race condition on the server that occurs in PXE operations that attempt multi-threaded network transfers. For example:
A high number of logical processors (32+ logical processors)
Multiple clients connect to a single PXE
To fix this issue, install the May 2016 update rollup for Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2 (KB3156418).
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Learn about the terminology that Microsoft uses to describe software updates.