Are the Arria V and Cyclone V hard memory controllers half rate capable?

The hard memory controller in ArriaV and Cyclone V devices only supports full-rate mode (Full-Rate).

ArriaV and Cyclone V devices are the first Altera devices to feature a hard memory controller. This IP will be UniPHY based IP.
Normally, when UniPHY is implemented as soft IP, only half rate mode (Half-Rate) is supported.

For details, search for the keyword "Protocol Support Matrix" in the document "External Memory Interface Handbook" at the following URL link and refer to it.
  https://www.altera.co.jp/ja_JP/pdfs/literature/hb/external-memory/emi.pdf