AVNET: MIG parameters for SP6 LX75T.
"The issue with running your MIG-generated design may be a BOARD-LEVEL ISSUE. The errata for this board (posted on the DRC) describes a known problem with the DDR3 interface and the default bitgen settings. By default the bitgen settings for any XPS project attach pulldowns to any unused signals on the FPGA. This breaks the FPGA designs using the MCBs. To fix this, change the bitgen settings to allow unused pins to float. Add this line to the bitgen settings file (bitgen.ut) of your project:
-g UnusedPin: Pullnone (remove the space between the ':' and 'P')
This should fix the problem."
Xor.kruger, да... это очень распространенная ошибка