http://wccftech.com/amd-rx-vega-56-serious-performance-upgrade-with-vega-64-bios/

Something pretty interesting was spotted by the folks over at Chiphell forums (via Videocardz) when they tried to unlock the newly launched RX Vega 56 into a full fledged Vega 64 graphics card. While this trick, apparently, no longer works, users will still get quite a significant speedup because the Vega 64 bios will enable higher turbo clocks resulting in much faster performance of the Vega  56. In fact, according to the same report it is only 2% slower than a Vega 64 and faster than the same once overclocked further.

Unlocking AMD dies to their full fledged counterparts has become more or less a tradition – and one that has been fairly successful in the past few generations. The first few batches after launch usually consist of healthy dies that have had CUs locked by BIOS to convert them into their younger siblings. In fact, Overclockers UK has actually sold unlocked cards like this with a full fledged warranty. With Vega 56 however, it looks like that is not the case and the dies are the natural result of yield theory with the inactive section not capable of spinning up.