For those unaware, in the world of arcade preservation, "DejaVu" usually refers to a specific ** decrypted ROM set for the SEGA NAOMI platform**.
SEGA NAOMI games used a specific encryption method (often involving a specific Hitachi CPU and encryption keys stored on the game cart/GDIM). For years, running these games on emulators like NullDC or Makaron was impossible without decrypted ROMs.
Back in the "scene" days (around 2008–2010), a group or individual often associated with the handle "DejaVu" released decrypted versions of these games so they could be played on emulators without the original protection hardware.
If you must run an old 2008-era tool:
The term "93c86" refers to the 93C86 Serial EEPROM. This is a 16-bit, 2048-bit (256-byte) memory chip commonly used in arcade cartridges and consoles to store:
In the context of NAOMI or similar arcade boards (like the Triforce or Chihiro), the 93C86 often housed the specific cartridge key needed to unscramble the main program data.