Somebody (ISC I >>think<<) inserted some of the code for INed into the ROMs of the Perkin-Elmer Fox terminals to provide some assistance (which were 6800-based).  I never knew much about it, but it was the system the 68000 folks (Les Crudele, Nich Trudenick et al) used during core development.  It all ran on a PDP-11/70, which was running Interactive's V6 port that their group controlled in the back, basically unnoticed.  Les told me that the system was pretty responsive, even with the load they put on it of editing and text processing, much more responsive than the resources Motorola corporate offered them.  This was all important because the 6809 was the "corporate" project and what would become the 68000 was purely an unamed skunkworks project, basically hidden away from the core management structure as an experiment/bet that they could do it (a story told elsewhere and while UNIX rely on the results, was not part of UNIX's story directly other than a PDP-11/70 running UNIX was the system was used to create the processor).