This problem affects DDR2, DDR3, LPDDR2, QDR II, RLDRAM II, and RLDRAM 3 products.
When compiling your memory interface, you might receive warning messages resembling the following:
DQ I/O pins fed by DQS I/O pin "I/O pad mem_dqs[n]"
assigned different I/O standards -- it is recommended that all DQ
I/O pins fed by the same DQS I/O pin have the same I/O standard