This is the most reliable archive for ORSiO devices. Check the dedicated ORSiO b731 discussion thread for user-uploaded firmware links and custom builds.
Please be aware that there is also an OKI B731dn printer which shares a similar model number. Ensure you are looking for e-reader firmware and not printer drivers. ORSiO b731 - 4PDA
features a 6-inch E-Ink Vizplex screen and is powered by a processor.
Firmware updates historically improved support for the fb2 format , adding features like bookmarks and better navigation. Caution: