Anything to do with the 604 requiring a 64bit memory controller, while the 603 can use the 32bit one on the BPPC?
jackpot!
well done!
pin-compatible was never a issue as most are n/c on the Blizzard card anyway. but there are many signals that are not tied it does not seem to effect the 603e or does not show up but never the less even on the 603e their should be tied. this will effect other processors which some signals are marked as critical when useing a different processor on the Blizzaard card.
according to some of the docs iv read *all* signal should be tied if not used. the Blizzard PPC card has as many as 65 signals from my last count but it seems only about half of the 65 signals i can get away with not being tied.
critical signals must be addressed otherwise the processor will not work.
i can add some of the missing tracks on the PCB and tied some of the critcal signals but this can only be done with BGA socket.