Depending on the core speed grade, VCC can be 0.85V or 0.9V.

Note that other power supplies may also have different voltage levels depending on the speed grade of the core.

For details, refer to the Stratix V Device Datasheet, pages 5 to 7 at the URL link below.
 https://www.altera.com/en_US/pdfs/literature/hb/stratix-v/stx5_53001.pdf