Dr. K. Hudson Lead Architect, NEC Home Electronics
I notice you mentioned "syscard3.pce" — that’s a for the PC-Engine / TurboGrafx CD (and PC Engine Duo / Super CD-ROM² systems). syscard3.pce
Engineering teams have included a failsafe diagnostic routine accessible without a CD-ROM loaded. This is not intended for end-users but is documented here for repair technicians. Dr. K. Hudson Lead Architect