This message was posted on behalf of Intel Corporation
Thank you for contacting Intel Customer Support.
I would like to share the Operating System Compatibility for Intel® Server Board S2600GL/GZ, Windows 8.1 is not a validated operating system for you server board.
I'm not looking for "supported" or "validated"...I'm looking for if someone has installed it and had it run in a stable condition
8.1 and Windows Server 2012R2 use the same kernel. Try installing latest chipset drivers and other ones per 2012R2