|'''I/O'''||'''Decoded as'''||'''Port'''||'''Read'''||'''Write'''
|-
|#78XX||?||[[CPC4MB|4Mb Memory extension]]||?-||Write
|-
|#79XX||?||[[CPC4MB|4Mb Memory extension]]||?-||Write
|-
|#7AXX||?||[[CPC4MB|4Mb Memory extension]]||?-||Write
|-
|#7BXX||?||[[CPC4MB|4Mb Memory extension]]||?-||Write
|-
|#7CXX||?||[[CPC4MB|4Mb Memory extension]]||?-||Write
|-
|#7DXX||?||[[CPC4MB|4Mb Memory extension]]||?-||Write
|-
|#7EXX||?||[[CPC4MB|4Mb Memory extension]]||?-||Write
|-
|#7FXX||?||[[CPC4MB|4Mb Memory extension]]||?-||Write
|-
|#7FXX||?||[[Dk'tronics memory expansion]]||-||Write|-|#7FXX||?||[[Dobbertin Memory Expansion]]||-||Write|-|#7FXX||%0111xxxx xxxxxxxx||[[Gate Array]]|| -||Write
|-
|#BCXX||%x0xxxx00 xxxxxxxx||6845 [[CRTC]] Address-Register|| - ||Write