Here is an example of mamediff.exe output;
game (
name aafb
description "All American Football (rev E)"
year 1989
manufacturer "Leland Corp."
rom ( name 15603-01.u4t size 65536 crc cdc9c09d )
rom ( name 15604-01.u5t size 65536 crc 3c03e92e )
rom ( name 15605-01.u6t size 65536 crc cdf7d19c )
rom ( name 15606-01.u7t size 65536 crc 8eeb007c )
rom ( name 24000-02.u3 size 8192 crc 52df0354 )
rom ( name 24001-02.u2t size 65536 crc 9b20697d )
rom ( name 24002-02.u3t size 65536 crc bbb92184 )
rom ( name 24002-02.u8t size 65536 crc 3d9747c9 )
rom ( name 24004-02.u67 size 16384 crc cd7a3338 )
rom ( name 24005-02.u68 size 16384 crc 8ea75319 )
rom ( name 24006-01.u69 size 16384 crc 6a576aa9 )
rom ( name 24007-01.u70 size 16384 crc 40e46aa4 )
rom ( name 24008-01.u90 size 16384 crc 4538bc58 )
rom ( name 24009-02.u91 size 16384 crc b857a1ad )
rom ( name 24010-01.u92 size 16384 crc 78705f42 )
rom ( name 24011-02.u93 size 32768 crc 71f4425b flags nodump )
rom ( name 24012-02.u94 size 32768 crc b2499547 flags nodump )
rom ( name 24013-02.u95 size 32768 crc 0a604e0d flags nodump )
rom ( name 24016-01.u13 size 65536 crc 6997025f )
rom ( name 24017-01.u14 size 65536 crc a48bd721 )
rom ( name 24018-01.u15 size 65536 crc 76eb6077 )
rom ( name 24019-01.u25 size 65536 crc 9e344768 )
rom ( name 24020-01.u26 size 65536 crc 0788f2a5 )
rom ( name 24021-01.u27 size 65536 crc 94081899 )
rom ( name aafbu58t.bin size 65536 crc fa75a4a0 )
rom ( name aafbu59t.bin size 65536 crc ab6a606f )
)
game (
name aafbb
description "All American Football (rev B)"
year 1989
manufacturer "Leland Corp."
rom ( name 24014-02.u58 size 65536 crc 5db4a3d0 )
rom ( name 24015-02.u59 size 65536 flags nodump )
)
game (
name aafbd2p
description "All American Football (rev D, 2 Players)"
year 1989
manufacturer "Leland Corp."
rom ( name 26000-01.u3 size 8192 crc 98c06c63 )
rom ( name 26001-01.2t size 65536 crc f118b9b4 )
rom ( name 26014-01.58t size 65536 crc 79fd14cd )
rom ( name 26015-01.59t size 65536 crc 3b0382f0 )
)
Clrmamepro locks merge setting to 'non-merged sets'.
I noticed the output also doesn't have an 'header' section. I tried to add one myself but failed probably because I was trying to add an listxml header to an listinfo dat. (If I understand correctly). Whether forcing 'merge' type via 'header' of listinfo.dat is possible or would have worked in Clrmamepro on this occasion I don't know.
So, that is why I used datutil to convert the .dat over to listxml format so I could add the 'header' forcing message which gets me around this issue I was having with Clrmamepro.
I suppose you can probably see what the *real* cause of the problem is though. I suspect it is something to do with no tags like 'clone of' and 'parent of' in the .dat, but again I am not that clued up, so...