@emard @charlesap OK, thinking about the address bus stability with a fresh mind this morning lead to a minimal, 2 line fix to the RISC5 core and now it seems to work (in simulation) as it should. It continues to led=0x40, "Directory traversal complete" when te simulation time (200ms) ran out.
Will do a longer run, but it seems we are there on the simulation side.
How about a test without video at 125MHz? It would be good to know if that boots to the expected leds.
My simulation now ran for 400ms, but it is still doing stuff with the file system at that time.
ERROR: Failed to pack flipflop 'controller.dbi_FF._TECHMAP_REPLACE_' with 'syn_useioff' set into IOLOGIC. ERROR: Packing design failed.