7 Unknown
6 Unknown (Discology utility uses it - does it choose RAM in 32K blocks instead of 64K blocks??)
5 Ramcard - Ram disabled : When 1, bits allow mapping byte in 7Fxx to access BANK selected by byte 2..0 define which 64k block of SP512 RAM to select(Paging ok 32K). When 0, chooses internal 7Fxx has not effect (note DK'Tronic 64K RAM of CPC464for CPC 464 may work in this case). 4 UnknownWhen 1, disable all internal and external RAM. Reserved for future use 3 UnknownRam expansion - Rom disable when 1
2..0 Used to choose the 64K block of the SP512 to select