It is different than normal interleave: A = KS ROM B = EXT ROM byte 1 of A byte 0 of A byte 1 of B byte 0 of B byte 3 of A byte 2 of A byte 3 of B. Marble Blast Emerald there. Can INTRL.EXE do this interleaving? Pinnacle Studio Wedding Project more. YES so, let's try with real CD32 Roms CD32 KS ROM v3.1 - CRC32 1E62D4A5 CD32 extended ROM - CRC32 87746BE2 INTERL CD32 KS ROM v3.1 + CD32 extended ROM Bad checksum: i got C9DA5A71 instead of A4FBC94A INTERL CD32 extended ROM + CD32 KS ROM v3.1 Bad checksum: i got 4BBF6ACC instead of A4FBC94A CD32 ROM (KS + extended) REAL DUMP definition taken from WinUAE source so i think that this. Thanks for the info Toni, in the meantime i solved the mistery by myself: take CD32 extended ROM and do this: FOR x=0 TO 65535 DO takebyte((x*4)+1) takebyte((x*4)+0) the result is file A take CD32 KS ROM v3.1 and do this: FOR x=0 TO 65535 DO takebyte((x*4)+1) takebyte((x*4)+0) the result is file B take CD32 extended ROM and do this: FOR x=0 TO 65535 DO takebyte((x*4)+3) takebyte((x*4)+2) the result is file C take CD32 KS ROM v3. Numark Dxm 01 Driver. 1 and do this: FOR x=0 TO 65535 DO takebyte((x*4)+3) takebyte((x*4)+2) the result is file D binary copy A+B+C+D and the result is REAL CD32 Rom dump i put in The Zone! A zip file (REAL_CD32_CONVERTER.ZIP) that automates the process (you must only supply plain CD32 rom named as 'CD32.ROM' and you will get 'CD32REAL.ROM') Thanks again for the info and for the help, i think that all topic are interesting if they help to better understand the operation of the emulator or real Amiga hardware.