General Description: Even though all Virtex-II devices (except 2V8000) are available in a -6 speed grade, I am not able to select this speed grade in the Foundation 4.2i software when using the VHDL flow.
The Foundation 4.2i software release is integrated with FPGA Express version 3.6.1, which has not been upgraded to include the -6 speed grade for Virtex-II devices.
To work around this issue:
1. Press the Synthesis button in Foundation Project Manager.
2. Select your part and package, and select a speed grade of "-5".
3. After synthesis is complete, go to the Windows Start menu -> Xilinx Foundation 4 -> Accessories, and run Design Manager. (Design Manager should open with your Foundation project already loaded.)
4. Select the revision on which you are working, and select "Set Part" from the Design menu.
5. In this Set Part dialog box, you will be able to select the -6 speed grade.
6. Once this part is selected, you may select "Implement" from the Design menu to implement your design in this part.
You can work around this by manually adding the -6 speed grade to the "virtex2.pts" file in the $Xilinx/express/lib directory.