The ISE Design Suite 12.1 Release Notes and Licensing Guide found on xilinx.com contains installation instructions, system requirements, and other general information. This Known Issues Answer Record is a supplement to the release notes documentation and contains links to information on known issues in the design tools that might be resolved in future versions.
NOTE: For IP Known Issues, see the IP Release Notes Guide:
http://www.xilinx.com/support/documentation/ip_documentation/xtp025.pdf