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AR# 56541

14.6, IBERT - Incorrect DRC for IBERT Line Rate


The Virtex-6 SX475T -1 speed grade device has an incorrect DRC check in 14.6 GTX IBERT which limits the GTX line rate to 4 Gb/s. Similarly, the -2/-3 speed grade DRC allows a rate of up to 10.31 Gb/s.

The rate limits shown in the Virtex-6 data sheet (DS152) are correct. The -1 speed grade GTX should be limited to 5 Gb/s and the -2/-3 speed grade GTX should be limited to 6.6 Gb/s.


To work around the DRC limiting the -1 speed grade line rate, you should generate a -2 speed grade NGC using the CORE Generator tool and include it in your design:

  1. Create a CORE Generator project targeting the -2 speed grade device.
  2. Generate only the NGC file when finishing the core; uncheck the generate bitstream combo box.
  3. Navigate to the implement directory of the project and edit the "implemnt.sh" or "implement.bat" script to reflect the -1 speed grade device.
  4. Source the "implement" script you have edited when running Place and Route and generate a bitstream.

Following these steps will get the design past the erroneous DRC check while still including the proper routing and timing for the -1 speed grade device.

AR# 56541
Date 09/26/2013
Status Active
Type Known Issues
  • Virtex-6
  • ISE Design Suite - 14.6
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