From our friend ArcadeHacker, a new blog post:
Read more in detail from the link aboveDear all, after some lengthy testing we are happy to release full details on the security programing of the Hitachi FD1089 / FD1094 cpus used in Sega's System 16 / 18 / 24 / X motherboards.
This guide is the result of several years of work by a small group of arcade enthusiasts to unravel the secrets of the security implementation found in one of the most loved and popular arcade game platforms. Thanks to this work it is now possible to fully preserve most Sega 16 bit systems enabled with security as fully working unmodified originals.
Unlike previous projects this time we recommend the usage of a dedicated pcb to interface with the chips due to the high pin count involved in the programming.
Additional details of the inner workings of Sega's FD security modules will be published over time in this blog. Work on the earlier MC 8 bit modules used in some System 1 / 2 boards and sound of Sega 16 is still in progress and will be published when completed.