The FEP on 3600 was 68k - on Ivories FEP is normal Ivory program started from ROM.
The MacIvories and UX-series embeddable systems run FEP from their ROMs, but both FEP and OS on those use "Embedded" hardware model, where they use a memory-based buffer to provide "stream" used to communicate with "Life Support" software.
The VLM (Ivory rev5) systems, aka OpenGenera, don't have proper FEP (only a lisp debugger image) and in their case the LifeSupport application contains an embedded CPU implementation and implements loading of world files directly (thus bypassing the main purpose of FEP)
The MacIvories and UX-series embeddable systems run FEP from their ROMs, but both FEP and OS on those use "Embedded" hardware model, where they use a memory-based buffer to provide "stream" used to communicate with "Life Support" software.
The VLM (Ivory rev5) systems, aka OpenGenera, don't have proper FEP (only a lisp debugger image) and in their case the LifeSupport application contains an embedded CPU implementation and implements loading of world files directly (thus bypassing the main purpose of FEP)