Old rom code:

7D61H  (3AH) LDA FAC1H
7D64H  (57H) MOV D,A
7D65H  (CDH) CALL 7EE1H     ; Calculate physical RAM available
7D68H  (BAH) CMP D
7D69H  (C2H) JNZ 7DE7H      ; Cold boot routine


7D6CH  (CDH) CALL F605H     ; Detect Option ROM


new rom code

7D61H  JMP 7D6CH  (C3)
7D64H  NOP
7D65H  NOP
7D66H  NOP
7D67H  NOP
7D68H  NOP
7D69H  NOP
7D6AH  NOP
7D6BH  NOP

7D6CH  (CDH) CALL F605H     ; Detect Option ROM