I have changed jumper J100 on the MB from INT to EXT and the J100 on the processor card is set to enable MAPROM.
Both J100 and J104 need to be set to EXT. Also, I'd disable the MAPROM for testing purposes. (Don't try to enable it until after you get the rest working!) Also, set the ROMSPEED jumpers to the slowest (highest) settings. Again, try speeding them up once you get the system able to boot. But start testing at the slowest settings possible.
I have looked at Warren Block's site but can't seem to find all the jumpers he mentions (eg. J488)
Not all jumpers are on all versions of the A4000 motherboard, so I wouldn't worry about it. My 4000D is missing several of the jumpers and connections mentioned.
