So, let’s say you’ve got a “32-core workstation with 4 Xeon processors.” What version of Windows should you get?

To answer that question, you need to understand how the different Windows editions support processors.

• Windows 7 Professional, Enterprise, and Ultimate support up to two physical processors.
• Windows Server 2012 is licensed per processor. A license supports up to two processors, so for a four-processor machine, you need two licenses (of Windows Server 2012 Standard).

From Microsoft, here’s some information about Windows licenses and multiple processors:

• Windows 7
  PCs with multi-core processors:
  Windows 7 was designed to work with today’s multi-core processors. All 32-bit versions of Windows 7 can support up to 32 processor cores, while 64-bit versions can support up to 256 processor cores.

  PCs with multiple processors (CPUs):
  Commercial servers, workstations, and other high-end PCs may have more than one physical processor. Windows 7 Professional, Enterprise, and Ultimate allow for two physical processors, providing the best performance on these computers. Windows 7 Starter, Home Basic, and Home Premium will recognize only one physical processor.

• Windows Server 2012
  How do I calculate the number of licenses I need for a server?

  The number of licenses you will need depends on the number of physical processors on the server and the number of server instances that you will be running. (This only applies for Standard edition because Datacenter edition allows for unlimited VMs.) The larger of these two numbers determines the number of total licenses required.

  Determining the number of physical processor licenses
  Each license covers up to two physical processors, so to determine the number of licenses needed to
  fully license a physical server, simply count the number of physical processors in the server, divide that number by two and that tells you the number of licenses that will be needed.

  Here are some examples:

  • You have a 2-processor server. 2 physical processors / 2 (number of processors covered by a license) equals 1. You will need one license to cover a 2-processor server.
  • You have a 4-processor server. 4 physical processors / 2 (number of processors covered by a license) equals 2. You will need two licenses to cover a 4-processor server.
  • You have an 8-processor server. 8 physical processors / 2 (number of processors covered by a
    license) equals 4. You will need four licenses to cover an 8-processor server.

Here’s some more reading about Windows Server, licensing, and multiple processors:

• Windows Server 2012 Licensing In Detail
• Caps and Limits on Hardware Resources in Microsoft Windows and Red Hat Enterprise Linux
• Which version of Windows Server 2012 should I choose?