R&D precedes T&E . . . preferably. Check the Memory Map in the 475/605 DevNotes to see if there's any possibility of having hacked in RAM shoehorned in there. A machine with SIMM slots for Bank A will poll, test & map available memory. The startup routine of a soldered Bank A machine likely assumes, tests and maps only the standard allotment.

I'm hoping to be proved wrong. }